diff --git a/arch/platform/cooja/contiki-conf.h b/arch/platform/cooja/contiki-conf.h
index b15ea4636..970eddbb8 100644
--- a/arch/platform/cooja/contiki-conf.h
+++ b/arch/platform/cooja/contiki-conf.h
@@ -33,6 +33,11 @@
 #ifndef CONTIKI_CONF_H_
 #define CONTIKI_CONF_H_
 
+/* include the project config */
+#ifdef PROJECT_CONF_PATH
+#include PROJECT_CONF_PATH
+#endif /* PROJECT_CONF_PATH */
+
 #ifdef INCLUDE_SUBPLATFORM_CONF
 #include "subplatform-conf.h"
 #endif /* INCLUDE_SUBPLATFORM_CONF */
@@ -137,10 +142,4 @@ typedef uint64_t rtimer_clock_t;
 #define RF_CHANNEL                     26
 #define NETSTACK_RADIO_MAX_PAYLOAD_LEN 125
 
-/* include the project config */
-#ifdef PROJECT_CONF_PATH
-#include PROJECT_CONF_PATH
-#endif /* PROJECT_CONF_PATH */
-
-
 #endif /* CONTIKI_CONF_H_ */
diff --git a/arch/platform/jn516x/contiki-conf.h b/arch/platform/jn516x/contiki-conf.h
index f464d8773..620e55674 100644
--- a/arch/platform/jn516x/contiki-conf.h
+++ b/arch/platform/jn516x/contiki-conf.h
@@ -33,6 +33,11 @@
 #ifndef CONTIKI_CONF_H_
 #define CONTIKI_CONF_H_
 
+/* include the project config */
+#ifdef PROJECT_CONF_PATH
+#include PROJECT_CONF_PATH
+#endif /* PROJECT_CONF_PATH */
+
 #ifdef PLATFORM_CONF_H
 #include PLATFORM_CONF_H
 #else
@@ -49,9 +54,4 @@
 #define CCM_STAR_CONF ccm_star_driver_jn516x
 #endif /* CCM_STAR_CONF */
 
-/* include the project config */
-#ifdef PROJECT_CONF_PATH
-#include PROJECT_CONF_PATH
-#endif /* PROJECT_CONF_PATH */
-
 #endif /* CONTIKI_CONF_H_ */
diff --git a/arch/platform/jn516x/dev/exceptions.c b/arch/platform/jn516x/dev/exceptions.c
index 2991de639..172118a97 100644
--- a/arch/platform/jn516x/dev/exceptions.c
+++ b/arch/platform/jn516x/dev/exceptions.c
@@ -36,6 +36,7 @@
 #include <jendefs.h>
 #include <AppHardwareApi.h>
 #include <MicroInt.h>
+#include "contiki.h"
 #include "exceptions.h"
 
 #ifndef EXCEPTION_STALLS_SYSTEM
diff --git a/arch/platform/native/contiki-conf.h b/arch/platform/native/contiki-conf.h
index f30e19f9d..2e9526cb2 100644
--- a/arch/platform/native/contiki-conf.h
+++ b/arch/platform/native/contiki-conf.h
@@ -33,6 +33,11 @@
 #ifndef CONTIKI_CONF_H_
 #define CONTIKI_CONF_H_
 
+/* include the project config */
+#ifdef PROJECT_CONF_PATH
+#include PROJECT_CONF_PATH
+#endif /* PROJECT_CONF_PATH */
+
 #include <inttypes.h>
 #ifndef WIN32_LEAN_AND_MEAN
 #include <sys/select.h>
@@ -94,9 +99,4 @@ typedef unsigned long clock_time_t;
 /* Not part of C99 but actually present */
 int strcasecmp(const char*, const char*);
 
-/* include the project config */
-#ifdef PROJECT_CONF_PATH
-#include PROJECT_CONF_PATH
-#endif /* PROJECT_CONF_PATH */
-
 #endif /* CONTIKI_CONF_H_ */
diff --git a/arch/platform/nrf52dk/contiki-conf.h b/arch/platform/nrf52dk/contiki-conf.h
index f52bf48d2..f8d7f8b1d 100644
--- a/arch/platform/nrf52dk/contiki-conf.h
+++ b/arch/platform/nrf52dk/contiki-conf.h
@@ -61,7 +61,11 @@
 
 /* 6LoWPAN */
 #define SICSLOWPAN_CONF_MAC_MAX_PAYLOAD         1280
+
+#ifndef SICSLOWPAN_CONF_FRAG
 #define SICSLOWPAN_CONF_FRAG                    0     /**< We don't use 6LoWPAN fragmentation as IPSP takes care of that for us.*/
+#endif
+
 #define SICSLOWPAN_FRAMER_HDRLEN                0     /**< Use fixed header len rather than framer.length() function */
 
 /* Packet buffer */
diff --git a/arch/platform/sky/contiki-conf.h b/arch/platform/sky/contiki-conf.h
index 6bce536ec..52fc596a8 100644
--- a/arch/platform/sky/contiki-conf.h
+++ b/arch/platform/sky/contiki-conf.h
@@ -3,6 +3,11 @@
 #ifndef CONTIKI_CONF_H
 #define CONTIKI_CONF_H
 
+/* include the project config */
+#ifdef PROJECT_CONF_PATH
+#include PROJECT_CONF_PATH
+#endif /* PROJECT_CONF_PATH */
+
 #ifdef PLATFORM_CONF_H
 #include PLATFORM_CONF_H
 #else
@@ -33,9 +38,4 @@
 #define AES_128_CONF cc2420_aes_128_driver
 #endif /* AES_128_CONF */
 
-/* include the project config */
-#ifdef PROJECT_CONF_PATH
-#include PROJECT_CONF_PATH
-#endif /* PROJECT_CONF_PATH */
-
 #endif /* CONTIKI_CONF_H */
diff --git a/examples/6tisch/6p-packet/project-conf.h b/examples/6tisch/6p-packet/project-conf.h
index 70ce6c7ad..0381217c6 100644
--- a/examples/6tisch/6p-packet/project-conf.h
+++ b/examples/6tisch/6p-packet/project-conf.h
@@ -32,7 +32,6 @@
 #define _PROJECT_CONF_H_
 
 #define CONTIKI_WITH_RPL     0
-#undef UIP_CONF_IPV6_RPL
 #define UIP_CONF_IPV6_RPL    0
 #define UIP_CONF_ND6_SEND_RA 0
 
diff --git a/examples/6tisch/etsi-plugtest-2017/project-conf.h b/examples/6tisch/etsi-plugtest-2017/project-conf.h
index d7761bf90..894a49aba 100644
--- a/examples/6tisch/etsi-plugtest-2017/project-conf.h
+++ b/examples/6tisch/etsi-plugtest-2017/project-conf.h
@@ -59,21 +59,17 @@
 /*******************************************************/
 
 /* IEEE802.15.4 PANID */
-#undef IEEE802154_CONF_PANID
 #define IEEE802154_CONF_PANID 0x81a5
 
 /* Do not start TSCH at init, wait for NETSTACK_MAC.on() */
-#undef TSCH_CONF_AUTOSTART
 #define TSCH_CONF_AUTOSTART 0
 
 /* 6TiSCH minimal schedule length.
  * Larger values result in less frequent active slots: reduces capacity and saves energy. */
-#undef TSCH_SCHEDULE_CONF_DEFAULT_LENGTH
 #define TSCH_SCHEDULE_CONF_DEFAULT_LENGTH 11
 
 #if WITH_SECURITY
 /* Enable security */
-#undef LLSEC802154_CONF_ENABLED
 #define LLSEC802154_CONF_ENABLED 1
 #define LLSEC802154_CONF_USES_EXPLICIT_KEYS 0
 #define LLSEC802154_CONF_USES_FRAME_COUNTER 0
@@ -89,19 +85,14 @@
 
 #define TSCH_CONF_MAC_MAX_FRAME_RETRIES       3
 
-#undef TSCH_CONF_DEFAULT_HOPPING_SEQUENCE
 #define TSCH_CONF_DEFAULT_HOPPING_SEQUENCE (uint8_t[]){ 20 }
 //#define TSCH_CONF_DEFAULT_HOPPING_SEQUENCE TSCH_HOPPING_SEQUENCE_16_16
 
-#undef TSCH_PACKET_CONF_EACK_WITH_SRC_ADDR
 #define TSCH_PACKET_CONF_EACK_WITH_SRC_ADDR 1
 
-#undef TSCH_PACKET_CONF_EB_WITH_SLOTFRAME_AND_LINK
 #define TSCH_PACKET_CONF_EB_WITH_SLOTFRAME_AND_LINK 1
 
-#undef TSCH_CONF_EB_PERIOD
 #define TSCH_CONF_EB_PERIOD (1 * CLOCK_SECOND)
-#undef TSCH_CONF_MAX_EB_PERIOD
 #define TSCH_CONF_MAX_EB_PERIOD (1 * CLOCK_SECOND)
 
 /*******************************************************/
@@ -126,14 +117,11 @@
 /* Needed for CC2538 platforms only */
 /* For TSCH we have to use the more accurate crystal oscillator
  * by default the RC oscillator is activated */
-#undef SYS_CTRL_CONF_OSC32K_USE_XTAL
 #define SYS_CTRL_CONF_OSC32K_USE_XTAL 1
 
 #define USB_SERIAL_CONF_ENABLE 1
 /* USB serial takes space, free more space elsewhere */
-#undef SICSLOWPAN_CONF_FRAG
 #define SICSLOWPAN_CONF_FRAG 0
-#undef UIP_CONF_BUFFER_SIZE
 #define UIP_CONF_BUFFER_SIZE 160
 
 #if CONTIKI_TARGET_SRF06_CC26XX
@@ -146,27 +134,22 @@
 
 /* Needed for cc2420 platforms only */
 /* Disable DCO calibration (uses timerB) */
-#undef DCOSYNCH_CONF_ENABLED
 #define DCOSYNCH_CONF_ENABLED 0
 /* Enable SFD timestamps (uses timerB) */
-#undef CC2420_CONF_SFD_TIMESTAMPS
 #define CC2420_CONF_SFD_TIMESTAMPS 1
 
 /*******************************************************/
 /******************* Configure 6LoWPAN/IPv6 ************/
 /*******************************************************/
 
-#undef UIP_CONF_IPV6_CHECKS
 #define UIP_CONF_IPV6_CHECKS 1
 
-#undef SICSLOWPAN_CONF_COMPRESSION
 #define SICSLOWPAN_CONF_COMPRESSION SICSLOWPAN_COMPRESSION_6LORH
 
 /*******************************************************/
 /********* Enable RPL non-storing mode *****************/
 /*******************************************************/
 
-#undef RPL_CONF_MOP
 #define RPL_CONF_MOP RPL_MOP_NON_STORING /* Mode of operation*/
 
 /*******************************************************/
@@ -183,7 +166,6 @@
 #define LOG_CONF_LEVEL_6TOP                        LOG_LEVEL_DBG
 #define TSCH_LOG_CONF_PER_SLOT                     1
 
-#undef TCPIP_CONF_ANNOTATE_TRANSMISSIONS
 #define TCPIP_CONF_ANNOTATE_TRANSMISSIONS          0
 
 #endif /* __PROJECT_CONF_H__ */
diff --git a/examples/http-socket/Makefile b/examples/http-socket/Makefile
index a0d2534e3..e63dacd84 100644
--- a/examples/http-socket/Makefile
+++ b/examples/http-socket/Makefile
@@ -3,5 +3,4 @@ CONTIKI=../..
 MODULES += os/net/app-layer/http-socket
 
 CONTIKI_WITH_RPL_LITE = 0
-CFLAGS += -DUIP_CONF_TCP=1
 include $(CONTIKI)/Makefile.include
diff --git a/examples/http-socket/project-conf.h b/examples/http-socket/project-conf.h
new file mode 100644
index 000000000..38f34be86
--- /dev/null
+++ b/examples/http-socket/project-conf.h
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2017, George Oikonomou - http://www.spd.gr
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+/*---------------------------------------------------------------------------*/
+#ifndef PROJECT_CONF_H_
+#define PROJECT_CONF_H_
+/*---------------------------------------------------------------------------*/
+#define UIP_CONF_TCP 1
+/*---------------------------------------------------------------------------*/
+#endif /* PROJECT_CONF_H_ */
diff --git a/examples/ip64-router/Makefile b/examples/ip64-router/Makefile
index 65bd6da74..a77652cfa 100644
--- a/examples/ip64-router/Makefile
+++ b/examples/ip64-router/Makefile
@@ -1,5 +1,4 @@
 all: ip64-router
 CONTIKI=../..
 
-CFLAGS += -DUIP_CONF_TCP=1
 include $(CONTIKI)/Makefile.include
diff --git a/examples/ip64-router/project-conf.h b/examples/ip64-router/project-conf.h
new file mode 100644
index 000000000..38f34be86
--- /dev/null
+++ b/examples/ip64-router/project-conf.h
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2017, George Oikonomou - http://www.spd.gr
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+/*---------------------------------------------------------------------------*/
+#ifndef PROJECT_CONF_H_
+#define PROJECT_CONF_H_
+/*---------------------------------------------------------------------------*/
+#define UIP_CONF_TCP 1
+/*---------------------------------------------------------------------------*/
+#endif /* PROJECT_CONF_H_ */
diff --git a/examples/ipso-objects/project-conf.h b/examples/ipso-objects/project-conf.h
index 4efe5c32f..075cd7444 100644
--- a/examples/ipso-objects/project-conf.h
+++ b/examples/ipso-objects/project-conf.h
@@ -43,17 +43,13 @@
 #define IPSO_TEMPERATURE example_ipso_temperature
 
 /* Increase rpl-border-router IP-buffer when using more than 64. */
-#undef REST_MAX_CHUNK_SIZE
 #define REST_MAX_CHUNK_SIZE            64
 
 /* Multiplies with chunk size, be aware of memory constraints. */
-#undef COAP_MAX_OPEN_TRANSACTIONS
 #define COAP_MAX_OPEN_TRANSACTIONS     4
 
 /* Filtering .well-known/core per query can be disabled to save space. */
-#undef COAP_LINK_FORMAT_FILTERING
 #define COAP_LINK_FORMAT_FILTERING     0
-#undef COAP_PROXY_OPTION_PROCESSING
 #define COAP_PROXY_OPTION_PROCESSING   0
 
 /* Enable client-side support for COAP observe */
diff --git a/examples/ipv6/coap-example/README.md b/examples/ipv6/coap-example/README.md
index bd884b52f..c0ca817ca 100644
--- a/examples/ipv6/coap-example/README.md
+++ b/examples/ipv6/coap-example/README.md
@@ -19,7 +19,6 @@ PRELIMINARIES
 
 - Make sure rpl-border-router has the same stack and fits into mote memory:
   You can disable RDC in border-router project-conf.h (not really required as BR keeps radio turned on).
-    #undef NETSTACK_CONF_RDC
     #define NETSTACK_CONF_RDC     nullrdc_driver
 - Alternatively, you can use the native-border-router together with the slip-radio.
 - For convenience, define the Cooja addresses in /etc/hosts
diff --git a/examples/ipv6/coap-example/project-conf.h b/examples/ipv6/coap-example/project-conf.h
index d62d3952b..d8a3b1122 100644
--- a/examples/ipv6/coap-example/project-conf.h
+++ b/examples/ipv6/coap-example/project-conf.h
@@ -41,47 +41,36 @@
 
 /* Custom channel and PAN ID configuration for your project. */
 /*
-   #undef RF_CHANNEL
    #define RF_CHANNEL                     26
-
-   #undef IEEE802154_CONF_PANID
    #define IEEE802154_CONF_PANID          0xABCD
  */
 
 /* IP buffer size must match all other hops, in particular the border router. */
 /*
-   #undef UIP_CONF_BUFFER_SIZE
    #define UIP_CONF_BUFFER_SIZE           256
  */
 
 /* Increase rpl-border-router IP-buffer when using more than 64. */
-#undef REST_MAX_CHUNK_SIZE
 #define REST_MAX_CHUNK_SIZE            48
 
 /* Estimate your header size, especially when using Proxy-Uri. */
 /*
-   #undef COAP_MAX_HEADER_SIZE
    #define COAP_MAX_HEADER_SIZE           70
  */
 
 /* Multiplies with chunk size, be aware of memory constraints. */
-#undef COAP_MAX_OPEN_TRANSACTIONS
 #define COAP_MAX_OPEN_TRANSACTIONS     4
 
 /* Must be <= open transactions, default is COAP_MAX_OPEN_TRANSACTIONS-1. */
 /*
-   #undef COAP_MAX_OBSERVERS
    #define COAP_MAX_OBSERVERS             2
  */
 
 /* Filtering .well-known/core per query can be disabled to save space. */
-#undef COAP_LINK_FORMAT_FILTERING
 #define COAP_LINK_FORMAT_FILTERING     0
-#undef COAP_PROXY_OPTION_PROCESSING
 #define COAP_PROXY_OPTION_PROCESSING   0
 
 /* Turn off DAO-ACK to make code smaller */
-#undef RPL_CONF_WITH_DAO_ACK
 #define RPL_CONF_WITH_DAO_ACK          0
 
 /* Enable client-side support for COAP observe */
diff --git a/examples/ipv6/json-ws/project-conf.h b/examples/ipv6/json-ws/project-conf.h
index 948724f7e..1135d7dd1 100644
--- a/examples/ipv6/json-ws/project-conf.h
+++ b/examples/ipv6/json-ws/project-conf.h
@@ -38,13 +38,10 @@
 #define JSON_WS_CONF_CALLBACK_PORT  80
 #define JSON_WS_CONF_CALLBACK_INTERVAL 120
 
-#undef WEBSERVER_CONF_INBUF_SIZE
 #define WEBSERVER_CONF_INBUF_SIZE 200
 
-#undef WEBSERVER_CONF_OUTBUF_SIZE
 #define WEBSERVER_CONF_OUTBUF_SIZE (UIP_TCP_MSS + 20 + 80)
 
-#undef WEBSERVER_CONF_CFS_CONNS
 #define WEBSERVER_CONF_CFS_CONNS 3
 
 #endif /* PROJECT_CONF_H_ */
diff --git a/examples/ipv6/multicast/project-conf.h b/examples/ipv6/multicast/project-conf.h
index 198f3f47b..7a59c7d13 100644
--- a/examples/ipv6/multicast/project-conf.h
+++ b/examples/ipv6/multicast/project-conf.h
@@ -49,13 +49,10 @@
 /* For Imin: Use 16 over CSMA, 64 over Contiki MAC */
 #define ROLL_TM_CONF_IMIN_1         64
 
-#undef UIP_MCAST6_ROUTE_CONF_ROUTES
 #define UIP_MCAST6_ROUTE_CONF_ROUTES 1
 
 /* Code/RAM footprint savings so that things will fit on our device */
-#undef NETSTACK_MAX_ROUTE_ENTRIES
 #define NETSTACK_MAX_ROUTE_ENTRIES   10
-#undef NBR_TABLE_CONF_MAX_NEIGHBORS
 #define NBR_TABLE_CONF_MAX_NEIGHBORS 10
 
 #endif /* PROJECT_CONF_H_ */
diff --git a/examples/ipv6/native-border-router/project-conf.h b/examples/ipv6/native-border-router/project-conf.h
index 2e97f3acf..c6c9e4f30 100644
--- a/examples/ipv6/native-border-router/project-conf.h
+++ b/examples/ipv6/native-border-router/project-conf.h
@@ -30,21 +30,17 @@
 #ifndef PROJECT_ROUTER_CONF_H_
 #define PROJECT_ROUTER_CONF_H_
 
-#undef UIP_FALLBACK_INTERFACE
 #define UIP_FALLBACK_INTERFACE rpl_interface
 
 /* use a non-default network driver */
-#undef NETSTACK_CONF_NETWORK
 #define NETSTACK_CONF_NETWORK sicslowpan_driver
 
 /* use a non-default MAC driver */
-#undef NETSTACK_CONF_MAC
 #define NETSTACK_CONF_MAC border_router_mac_driver
 
 
 #define SLIP_DEV_CONF_SEND_DELAY (CLOCK_SECOND / 32)
 
-#undef WEBSERVER_CONF_CFS_CONNS
 #define WEBSERVER_CONF_CFS_CONNS 2
 
 #define SERIALIZE_ATTRIBUTES 1
diff --git a/examples/ipv6/rpl-border-router/Makefile b/examples/ipv6/rpl-border-router/Makefile
index 8abb62a10..c8a40f681 100644
--- a/examples/ipv6/rpl-border-router/Makefile
+++ b/examples/ipv6/rpl-border-router/Makefile
@@ -16,12 +16,10 @@ PROJECT_SOURCEFILES += slip-bridge.c
 
 WITH_WEBSERVER=1
 ifeq ($(WITH_WEBSERVER),1)
-CFLAGS += -DUIP_CONF_TCP=1
 CFLAGS += -DWEBSERVER=1
 PROJECT_SOURCEFILES += httpd-simple.c
 else ifneq ($(WITH_WEBSERVER), 0)
 MODULES += $(WITH_WEBSERVER)
-CFLAGS += -DUIP_CONF_TCP=1
 CFLAGS += -DWEBSERVER=2
 endif
 
diff --git a/examples/ipv6/rpl-border-router/project-conf.h b/examples/ipv6/rpl-border-router/project-conf.h
index fda9acd88..63930dd77 100644
--- a/examples/ipv6/rpl-border-router/project-conf.h
+++ b/examples/ipv6/rpl-border-router/project-conf.h
@@ -39,4 +39,8 @@
 #define WEBSERVER_CONF_CFS_CONNS 2
 #endif
 
+#if WEBSERVER
+#define UIP_CONF_TCP 1
+#endif
+
 #endif /* PROJECT_ROUTER_CONF_H_ */
diff --git a/examples/ipv6/rpl-simple/project-conf.h b/examples/ipv6/rpl-simple/project-conf.h
index e20e3c2a1..b5c3c9991 100644
--- a/examples/ipv6/rpl-simple/project-conf.h
+++ b/examples/ipv6/rpl-simple/project-conf.h
@@ -31,23 +31,16 @@
 #define PROJECT_CONF_H_
 
 /* Network size and PAN-ID */
-
-#undef NBR_TABLE_CONF_MAX_NEIGHBORS
 #define NBR_TABLE_CONF_MAX_NEIGHBORS 25
 
-#undef NETSTACK_MAX_ROUTE_ENTRIES
 #define NETSTACK_MAX_ROUTE_ENTRIES 25
 
-#undef IEEE802154_CONF_PANID
 #define IEEE802154_CONF_PANID 0xf123
 
 /* Save some space */
-
-#undef SICSLOWPAN_CONF_FRAG
 #define SICSLOWPAN_CONF_FRAG 0
 
 #if MAC_CONF_WITH_TSCH
-
 /*******************************************************/
 /********************* Configure TSCH *********************/
 /*******************************************************/
@@ -61,23 +54,18 @@
 /*******************************************************/
 /******************* Configure TSCH ********************/
 /*******************************************************/
+#endif /* MAC_CONF_WITH_TSCH */
 
 /* TSCH per-slot logging */
-#undef TSCH_LOG_CONF_PER_SLOT
 #define TSCH_LOG_CONF_PER_SLOT 1
 
 /* Do not start TSCH at init, wait for NETSTACK_MAC.on() */
-#undef TSCH_CONF_AUTOSTART
 #define TSCH_CONF_AUTOSTART 0
 
 /* 6TiSCH minimal schedule length.
  * Larger values result in less frequent active slots: reduces capacity and saves energy. */
-#undef TSCH_SCHEDULE_CONF_DEFAULT_LENGTH
 #define TSCH_SCHEDULE_CONF_DEFAULT_LENGTH 3
 
-#undef TSCH_SCHEDULE_CONF_MAX_LINKS
 #define TSCH_SCHEDULE_CONF_MAX_LINKS 4
 
-#endif /* MAC_CONF_WITH_TSCH */
-
 #endif
diff --git a/examples/ipv6/rpl-tsch-sixtop/project-conf.h b/examples/ipv6/rpl-tsch-sixtop/project-conf.h
index 97a47b9dc..3fa3d548a 100755
--- a/examples/ipv6/rpl-tsch-sixtop/project-conf.h
+++ b/examples/ipv6/rpl-tsch-sixtop/project-conf.h
@@ -39,12 +39,8 @@
 /*******************************************************/
 /********* Enable RPL non-storing mode *****************/
 /*******************************************************/
-
-#undef UIP_CONF_MAX_ROUTES
 #define UIP_CONF_MAX_ROUTES 0 /* No need for routes */
-#undef RPL_CONF_MOP
 #define RPL_CONF_MOP RPL_MOP_NON_STORING /* Mode of operation*/
-#undef ORCHESTRA_CONF_RULES
 #define ORCHESTRA_CONF_RULES { &eb_per_time_source, &unicast_per_neighbor_rpl_ns, &default_common } /* Orchestra in non-storing */
 
 /*******************************************************/
@@ -60,19 +56,15 @@
 /* Needed for CC2538 platforms only */
 /* For TSCH we have to use the more accurate crystal oscillator
  * by default the RC oscillator is activated */
-#undef SYS_CTRL_CONF_OSC32K_USE_XTAL
 #define SYS_CTRL_CONF_OSC32K_USE_XTAL 1
 
 /* Needed for cc2420 platforms only */
 /* Disable DCO calibration (uses timerB) */
-#undef DCOSYNCH_CONF_ENABLED
 #define DCOSYNCH_CONF_ENABLED 0
 /* Enable SFD timestamps (uses timerB) */
-#undef CC2420_CONF_SFD_TIMESTAMPS
 #define CC2420_CONF_SFD_TIMESTAMPS 1
 
 /* Enable Sixtop Implementation */
-#undef TSCH_CONF_WITH_SIXTOP
 #define TSCH_CONF_WITH_SIXTOP 1
 
 /*******************************************************/
@@ -80,31 +72,24 @@
 /*******************************************************/
 
 /* TSCH logging. */
-#undef TSCH_LOG_CONF_PER_SLOT
 #define TSCH_LOG_CONF_PER_SLOT 1
 
 /* IEEE802.15.4 PANID */
-#undef IEEE802154_CONF_PANID
 #define IEEE802154_CONF_PANID 0xabcd
 
 /* Do not start TSCH at init, wait for NETSTACK_MAC.on() */
-#undef TSCH_CONF_AUTOSTART
 #define TSCH_CONF_AUTOSTART 0
 
 /* 6TiSCH schedule length */
-#undef TSCH_SCHEDULE_CONF_DEFAULT_LENGTH
 #define TSCH_SCHEDULE_CONF_DEFAULT_LENGTH 11
 
 #if WITH_SECURITY
 
 /* Enable security */
-#undef LLSEC802154_CONF_ENABLED
 #define LLSEC802154_CONF_ENABLED 1
 /* TSCH uses explicit keys to identify k1 and k2 */
-#undef LLSEC802154_CONF_USES_EXPLICIT_KEYS
 #define LLSEC802154_CONF_USES_EXPLICIT_KEYS 1
 /* TSCH uses the ASN rather than frame counter to construct the Nonce */
-#undef LLSEC802154_CONF_USES_FRAME_COUNTER
 #define LLSEC802154_CONF_USES_FRAME_COUNTER 0
 
 #endif /* WITH_SECURITY */
@@ -115,29 +100,20 @@
 
 #if CONTIKI_TARGET_Z1
 /* Save some space to fit the limited RAM of the z1 */
-#undef UIP_CONF_TCP
 #define UIP_CONF_TCP 0
-#undef QUEUEBUF_CONF_NUM
 #define QUEUEBUF_CONF_NUM 2
-#undef RPL_NS_CONF_LINK_NUM
 #define RPL_NS_CONF_LINK_NUM  2
-#undef NBR_TABLE_CONF_MAX_NEIGHBORS
 #define NBR_TABLE_CONF_MAX_NEIGHBORS 2
-#undef UIP_CONF_ND6_SEND_NA
 #define UIP_CONF_ND6_SEND_NA 0
-#undef SICSLOWPAN_CONF_FRAG
 #define SICSLOWPAN_CONF_FRAG 0
 
 #if WITH_SECURITY
 /* Note: on sky or z1 in cooja, crypto operations are done in S/W and
  * cannot be accommodated in normal slots. Use 65ms slots instead, and
  * a very short 6TiSCH minimal schedule length */
-#undef TSCH_CONF_DEFAULT_TIMESLOT_LENGTH
 #define TSCH_CONF_DEFAULT_TIMESLOT_LENGTH 65000
-#undef TSCH_SCHEDULE_CONF_DEFAULT_LENGTH
 #define TSCH_SCHEDULE_CONF_DEFAULT_LENGTH 2
 /* Reduce log level to make space for security on z1 */
-#undef TSCH_LOG_CONF_LEVEL
 #define TSCH_LOG_CONF_LEVEL 0
 #endif /* WITH_SECURITY */
 
diff --git a/examples/ipv6/rpl-tsch/project-conf.h b/examples/ipv6/rpl-tsch/project-conf.h
index 39b9f5a55..f3becfc5c 100644
--- a/examples/ipv6/rpl-tsch/project-conf.h
+++ b/examples/ipv6/rpl-tsch/project-conf.h
@@ -52,9 +52,7 @@
 /********* Enable RPL non-storing mode *****************/
 /*******************************************************/
 
-#undef RPL_CONF_MOP
 #define RPL_CONF_MOP RPL_MOP_NON_STORING /* Mode of operation*/
-#undef ORCHESTRA_CONF_RULES
 #define ORCHESTRA_CONF_RULES { &eb_per_time_source, &unicast_per_neighbor_rpl_ns, &default_common } /* Orchestra in non-storing */
 
 /*******************************************************/
@@ -73,9 +71,7 @@
 #define USB_SERIAL_CONF_ENABLE 1
 
 /* USB serial takes space, free more space elsewhere */
-#undef SICSLOWPAN_CONF_FRAG
 #define SICSLOWPAN_CONF_FRAG 0
-#undef UIP_CONF_BUFFER_SIZE
 #define UIP_CONF_BUFFER_SIZE 160
 
 #endif /* WITH_SHELL */
@@ -85,22 +81,18 @@
 /*******************************************************/
 
 /* IEEE802.15.4 PANID */
-#undef IEEE802154_CONF_PANID
 #define IEEE802154_CONF_PANID 0x81a5
 
 /* Do not start TSCH at init, wait for NETSTACK_MAC.on() */
-#undef TSCH_CONF_AUTOSTART
 #define TSCH_CONF_AUTOSTART 0
 
 /* 6TiSCH minimal schedule length.
  * Larger values result in less frequent active slots: reduces capacity and saves energy. */
-#undef TSCH_SCHEDULE_CONF_DEFAULT_LENGTH
 #define TSCH_SCHEDULE_CONF_DEFAULT_LENGTH 3
 
 #if WITH_SECURITY
 
 /* Enable security */
-#undef LLSEC802154_CONF_ENABLED
 #define LLSEC802154_CONF_ENABLED 1
 
 #endif /* WITH_SECURITY */
diff --git a/examples/ipv6/slip-radio/project-conf.h b/examples/ipv6/slip-radio/project-conf.h
index c8288f2b6..fc51e55ec 100644
--- a/examples/ipv6/slip-radio/project-conf.h
+++ b/examples/ipv6/slip-radio/project-conf.h
@@ -30,13 +30,10 @@
 #ifndef PROJECT_CONF_H_
 #define PROJECT_CONF_H_
 
-#undef QUEUEBUF_CONF_NUM
 #define QUEUEBUF_CONF_NUM          4
 
-#undef UIP_CONF_BUFFER_SIZE
 #define UIP_CONF_BUFFER_SIZE    140
 
-#undef UIP_CONF_ROUTER
 #define UIP_CONF_ROUTER                 0
 
 #define CMD_CONF_OUTPUT slip_radio_cmd_output
@@ -55,10 +52,8 @@
 /* Configuration for the slipradio/network driver. */
 #define NETSTACK_CONF_NETWORK slipnet_driver
 
-#undef NETSTACK_CONF_FRAMER
 #define NETSTACK_CONF_FRAMER no_framer
 
-#undef UART1_CONF_RX_WITH_DMA
 #define UART1_CONF_RX_WITH_DMA           1
 
 #endif /* PROJECT_CONF_H_ */
diff --git a/examples/platform-specific/jn516x/rpl/border-router/project-conf.h b/examples/platform-specific/jn516x/rpl/border-router/project-conf.h
index 2489905a6..2673d895e 100644
--- a/examples/platform-specific/jn516x/rpl/border-router/project-conf.h
+++ b/examples/platform-specific/jn516x/rpl/border-router/project-conf.h
@@ -40,7 +40,6 @@
 #endif
 
 /* Needed for slip-bridge */
-#undef SLIP_BRIDGE_CONF_NO_PUTCHAR
 #define SLIP_BRIDGE_CONF_NO_PUTCHAR 0
 
 #include "../common-conf.h"
diff --git a/examples/platform-specific/jn516x/rpl/coap-dongle-node/Makefile b/examples/platform-specific/jn516x/rpl/coap-dongle-node/Makefile
index eb183a1cd..1b13ef3e0 100644
--- a/examples/platform-specific/jn516x/rpl/coap-dongle-node/Makefile
+++ b/examples/platform-specific/jn516x/rpl/coap-dongle-node/Makefile
@@ -11,8 +11,6 @@ MODULES += os/lib/json
 PROJECTDIRS += .. ../tools
 PROJECT_SOURCEFILES += rpl-tools.c
 
-CFLAGS += -DWITH_COAP
-CFLAGS += -DUIP_CONF_TCP=0
 MODULES += os/net/app-layer/coap
 
 include $(CONTIKI)/Makefile.include
diff --git a/examples/platform-specific/jn516x/rpl/coap-dongle-node/project-conf.h b/examples/platform-specific/jn516x/rpl/coap-dongle-node/project-conf.h
index 4c2ecd648..a46f32f1c 100644
--- a/examples/platform-specific/jn516x/rpl/coap-dongle-node/project-conf.h
+++ b/examples/platform-specific/jn516x/rpl/coap-dongle-node/project-conf.h
@@ -34,6 +34,8 @@
 #ifndef __PROJECT_CONF_H__
 #define __PROJECT_CONF_H__
 
+#define UIP_CONF_TCP 0
+
 #include "../common-conf.h"
 
 #endif /* __PROJECT_CONF_H__ */
diff --git a/examples/platform-specific/jn516x/rpl/coap-dr1175-node/Makefile b/examples/platform-specific/jn516x/rpl/coap-dr1175-node/Makefile
index 3da7690db..9a393ff14 100644
--- a/examples/platform-specific/jn516x/rpl/coap-dr1175-node/Makefile
+++ b/examples/platform-specific/jn516x/rpl/coap-dr1175-node/Makefile
@@ -11,8 +11,6 @@ MODULES += os/lib/json
 PROJECTDIRS += .. ../tools
 PROJECT_SOURCEFILES += rpl-tools.c
 
-CFLAGS += -DWITH_COAP
-CFLAGS += -DUIP_CONF_TCP=0
 MODULES += os/net/app-layer/coap
 
 include $(CONTIKI)/Makefile.include
diff --git a/examples/platform-specific/jn516x/rpl/coap-dr1175-node/project-conf.h b/examples/platform-specific/jn516x/rpl/coap-dr1175-node/project-conf.h
index 4c2ecd648..a46f32f1c 100644
--- a/examples/platform-specific/jn516x/rpl/coap-dr1175-node/project-conf.h
+++ b/examples/platform-specific/jn516x/rpl/coap-dr1175-node/project-conf.h
@@ -34,6 +34,8 @@
 #ifndef __PROJECT_CONF_H__
 #define __PROJECT_CONF_H__
 
+#define UIP_CONF_TCP 0
+
 #include "../common-conf.h"
 
 #endif /* __PROJECT_CONF_H__ */
diff --git a/examples/platform-specific/jn516x/rpl/coap-dr1199-node/Makefile b/examples/platform-specific/jn516x/rpl/coap-dr1199-node/Makefile
index 97b61dd9c..32231f636 100644
--- a/examples/platform-specific/jn516x/rpl/coap-dr1199-node/Makefile
+++ b/examples/platform-specific/jn516x/rpl/coap-dr1199-node/Makefile
@@ -11,8 +11,6 @@ MODULES += os/lib/json
 PROJECTDIRS += .. ../tools
 PROJECT_SOURCEFILES += rpl-tools.c
 
-CFLAGS += -DWITH_COAP
-CFLAGS += -DUIP_CONF_TCP=0
 MODULES += os/net/app-layer/coap
 
 include $(CONTIKI)/Makefile.include
diff --git a/examples/platform-specific/jn516x/rpl/coap-dr1199-node/project-conf.h b/examples/platform-specific/jn516x/rpl/coap-dr1199-node/project-conf.h
index 4c2ecd648..a46f32f1c 100644
--- a/examples/platform-specific/jn516x/rpl/coap-dr1199-node/project-conf.h
+++ b/examples/platform-specific/jn516x/rpl/coap-dr1199-node/project-conf.h
@@ -34,6 +34,8 @@
 #ifndef __PROJECT_CONF_H__
 #define __PROJECT_CONF_H__
 
+#define UIP_CONF_TCP 0
+
 #include "../common-conf.h"
 
 #endif /* __PROJECT_CONF_H__ */
diff --git a/examples/platform-specific/jn516x/rpl/common-conf.h b/examples/platform-specific/jn516x/rpl/common-conf.h
index ce104a759..fb7b0d51c 100644
--- a/examples/platform-specific/jn516x/rpl/common-conf.h
+++ b/examples/platform-specific/jn516x/rpl/common-conf.h
@@ -61,22 +61,18 @@
 #define TSCH_CALLBACK_LEAVING_NETWORK tsch_rpl_callback_leaving_network
 
 /* TSCH per-slot logging */
-#undef TSCH_LOG_CONF_PER_SLOT
 #define TSCH_LOG_CONF_PER_SLOT 1
 
 /* Do not start TSCH at init, wait for NETSTACK_MAC.on() */
-#undef TSCH_CONF_AUTOSTART
 #define TSCH_CONF_AUTOSTART 0
 
 /* 6TiSCH minimal schedule length.
  * Larger values result in less frequent active slots: reduces capacity and saves energy. */
-#undef TSCH_SCHEDULE_CONF_DEFAULT_LENGTH
 #define TSCH_SCHEDULE_CONF_DEFAULT_LENGTH 3
 
 #if WITH_SECURITY
 
 /* Enable security */
-#undef LLSEC802154_CONF_SECURITY_LEVEL
 #define LLSEC802154_CONF_SECURITY_LEVEL 1
 
 #endif /* WITH_SECURITY */
@@ -103,21 +99,16 @@
 
 /* IEEE802.15.4 PANID and channel */
 
-#undef IEEE802154_CONF_PANID
 #define IEEE802154_CONF_PANID 0xabcd
 
-#undef MICROMAC_CONF_CHANNEL
 #define MICROMAC_CONF_CHANNEL 26
 
 /* UART Configuration */
 
-#undef UART_HW_FLOW_CTRL
 #define UART_HW_FLOW_CTRL 0
 
-#undef UART_XONXOFF_FLOW_CTRL
 #define UART_XONXOFF_FLOW_CTRL 1
 
-#undef UART_BAUD_RATE
 #define UART_BAUD_RATE UART_RATE_1000000
 
 #endif /* __COMMON_CONF_H__ */
diff --git a/examples/platform-specific/jn516x/tsch/common-conf-jn516x.h b/examples/platform-specific/jn516x/tsch/common-conf-jn516x.h
index 3f33730dc..568fd4b6d 100644
--- a/examples/platform-specific/jn516x/tsch/common-conf-jn516x.h
+++ b/examples/platform-specific/jn516x/tsch/common-conf-jn516x.h
@@ -36,49 +36,41 @@
 
 /* Shall we restart after exception, or stall?
  * in production code we should restart, so set this to 0 */
-#undef EXCEPTION_STALLS_SYSTEM
 #define EXCEPTION_STALLS_SYSTEM 1
 
  /* CoAP */
-#undef COAP_MAX_OPEN_TRANSACTIONS
 #define COAP_MAX_OPEN_TRANSACTIONS 4
 
-#undef REST_MAX_CHUNK_SIZE
 #define REST_MAX_CHUNK_SIZE      256
 
 /* Network config */
-#undef UIP_CONF_BUFFER_SIZE
 //#define UIP_CONF_BUFFER_SIZE   (REST_MAX_CHUNK_SIZE + UIP_LLH_LEN + UIP_IPUDPH_LEN + COAP_MAX_HEADER_SIZE)
 //#define UIP_CONF_BUFFER_SIZE   (REST_MAX_CHUNK_SIZE + 0 + 48 + 70)
 #define UIP_CONF_BUFFER_SIZE     1280 /* ipv6 required minimum */
 
 /* Queues */
-#undef QUEUEBUF_CONF_NUM
+#ifndef QUEUEBUF_CONF_NUM
 #define QUEUEBUF_CONF_NUM 32
+#endif
 
-#undef TSCH_QUEUE_CONF_NUM_PER_NEIGHBOR
 #define TSCH_QUEUE_CONF_NUM_PER_NEIGHBOR 32
 
-#undef TSCH_CONF_DEQUEUED_ARRAY_SIZE
 #define TSCH_CONF_DEQUEUED_ARRAY_SIZE 32
 
-#undef TSCH_QUEUE_CONF_MAX_NEIGHBOR_QUEUES
 #define TSCH_QUEUE_CONF_MAX_NEIGHBOR_QUEUES 8
 
 /* Radio */
 
-#undef ENABLE_COOJA_DEBUG
 #define ENABLE_COOJA_DEBUG 0
 
 /* max 3, min 0 */
 
-#undef UART_HW_FLOW_CTRL
 #define UART_HW_FLOW_CTRL 0
 
-#undef UART_XONXOFF_FLOW_CTRL
 #define UART_XONXOFF_FLOW_CTRL 1
 
-#undef UART_BAUD_RATE
+#ifndef UART_BAUD_RATE
 #define UART_BAUD_RATE UART_RATE_1000000
+#endif
 
 #endif /* __COMMON_CONF_JN516X_H__ */
diff --git a/examples/platform-specific/jn516x/tsch/common-conf.h b/examples/platform-specific/jn516x/tsch/common-conf.h
index 886ce4884..28c5e2835 100644
--- a/examples/platform-specific/jn516x/tsch/common-conf.h
+++ b/examples/platform-specific/jn516x/tsch/common-conf.h
@@ -40,30 +40,23 @@
 #define TSCH_LOG_CONF_PER_SLOT 1
 #define WITH_COAP_RESOURCES 0
 
-#undef ENABLE_COOJA_DEBUG
 #define ENABLE_COOJA_DEBUG 0
 
-#undef IEEE802154_CONF_PANID
 #define IEEE802154_CONF_PANID 0x5254
 
-#undef TSCH_CONF_DEFAULT_HOPPING_SEQUENCE
 #define TSCH_HOPPING_SEQUENCE_MY_SEQUENCE (uint8_t[]){17, 23, 15, 25, 19, 11, 13, 21}
 #define TSCH_CONF_DEFAULT_HOPPING_SEQUENCE TSCH_HOPPING_SEQUENCE_MY_SEQUENCE
 
-#undef TSCH_CONF_JOIN_MY_PANID_ONLY
 #define TSCH_CONF_JOIN_MY_PANID_ONLY 1
 
-#undef TSCH_CONF_AUTOSTART
 #define TSCH_CONF_AUTOSTART 0
 
 #define RPL_CALLBACK_PARENT_SWITCH tsch_rpl_callback_parent_switch
 #define RPL_CALLBACK_NEW_DIO_INTERVAL tsch_rpl_callback_new_dio_interval
 
 /* RPL Trickle timer tuning */
-#undef RPL_CONF_DIO_INTERVAL_MIN
 #define RPL_CONF_DIO_INTERVAL_MIN 12 /* 4.096 s */
 
-#undef RPL_CONF_DIO_INTERVAL_DOUBLINGS
 #define RPL_CONF_DIO_INTERVAL_DOUBLINGS 2 /* Max factor: x4. 4.096 s * 4 = 16.384 s */
 
 #define TSCH_CONF_EB_PERIOD (4 * CLOCK_SECOND)
@@ -90,33 +83,25 @@
 
 /* CoAP */
 
-#undef COAP_SERVER_PORT
 #define COAP_SERVER_PORT 5684
 
-#undef COAP_OBSERVE_RETURNS_REPRESENTATION
 #define COAP_OBSERVE_RETURNS_REPRESENTATION 1
 
 /* RPL */
-#undef UIP_CONF_ROUTER
 #define UIP_CONF_ROUTER                 1
 
 /* RPL storing mode */
-#undef RPL_CONF_MOP
 #define RPL_CONF_MOP RPL_MOP_STORING_NO_MULTICAST
 
 /* Default link metric */
-#undef RPL_CONF_INIT_LINK_METRIC
 #define RPL_CONF_INIT_LINK_METRIC 2 /* default 5 */
 
 #define RPL_CONF_MAX_INSTANCES    1 /* default 1 */
 #define RPL_CONF_MAX_DAG_PER_INSTANCE 1 /* default 2 */
 
 /* No RA, No NS */
-#undef UIP_CONF_TCP
 #define UIP_CONF_TCP             0
-#undef UIP_CONF_DS6_ADDR_NBU
 #define UIP_CONF_DS6_ADDR_NBU    1
-#undef UIP_CONF_UDP_CHECKSUMS
 #define UIP_CONF_UDP_CHECKSUMS   1
 
 /* Link-layer security */
@@ -130,21 +115,15 @@
 
 #if MAC_CONF_WITH_CSMA /* Configure Csma with ACK (default MAC) */
 
-#undef MICROMAC_CONF_CHANNEL
 #define MICROMAC_CONF_CHANNEL 26
 
-#undef MICROMAC_CONF_AUTOACK
 #define MICROMAC_CONF_AUTOACK 1
 
 /* increase internal radio buffering */
-#undef MIRCOMAC_CONF_BUF_NUM
 #define MIRCOMAC_CONF_BUF_NUM 4
 
 #endif /* MAC_CONF_WITH_CSMA */
 
-#undef CONTIKI_VERSION_STRING
-#define CONTIKI_VERSION_STRING "Contiki 3.x"
-
 #include "common-conf-jn516x.h"
 
 #endif /* __COMMON_CONF_H__ */
diff --git a/examples/platform-specific/jn516x/tsch/simple-sensor-network/node/Makefile b/examples/platform-specific/jn516x/tsch/simple-sensor-network/node/Makefile
index 9f06ae400..df37a89af 100644
--- a/examples/platform-specific/jn516x/tsch/simple-sensor-network/node/Makefile
+++ b/examples/platform-specific/jn516x/tsch/simple-sensor-network/node/Makefile
@@ -7,9 +7,6 @@ CONTIKI=../../../../../..
 
 PROJECTDIRS += .. ../../tools
 PROJECT_SOURCEFILES += rpl-tools.c
-CFLAGS += -DWITH_COAP
-CFLAGS += -DREST=coap_rest_implementation
-CFLAGS += -DUIP_CONF_TCP=0
 MAKE_MAC = MAKE_MAC_TSCH
 MODULES += os/net/app-layer/coap
 MODULES += os/services/orchestra os/lib/json
diff --git a/examples/platform-specific/jn516x/tsch/simple-sensor-network/node/project-conf.h b/examples/platform-specific/jn516x/tsch/simple-sensor-network/node/project-conf.h
index 4e08f561c..360fdef25 100644
--- a/examples/platform-specific/jn516x/tsch/simple-sensor-network/node/project-conf.h
+++ b/examples/platform-specific/jn516x/tsch/simple-sensor-network/node/project-conf.h
@@ -35,9 +35,9 @@
 #ifndef __PROJECT_CONF_H__
 #define __PROJECT_CONF_H__
 
-#include "../../common-conf.h"
-
-#undef UART_BAUD_RATE
+#define UIP_CONF_TCP 0
 #define UART_BAUD_RATE UART_RATE_115200
 
+#include "../../common-conf.h"
+
 #endif /* __PROJECT_CONF_H__ */
diff --git a/examples/platform-specific/jn516x/tsch/simple-sensor-network/rpl-border-router/Makefile b/examples/platform-specific/jn516x/tsch/simple-sensor-network/rpl-border-router/Makefile
index f5f3b009e..41c732ba2 100644
--- a/examples/platform-specific/jn516x/tsch/simple-sensor-network/rpl-border-router/Makefile
+++ b/examples/platform-specific/jn516x/tsch/simple-sensor-network/rpl-border-router/Makefile
@@ -9,9 +9,6 @@ PROJECT_SOURCEFILES += slip-bridge.c slip.c
 PROJECTDIRS += .. ../../tools
 PROJECT_SOURCEFILES += rpl-tools.c
 
-CFLAGS += -DWITH_COAP
-CFLAGS += -DREST=coap_rest_implementation
-CFLAGS += -DUIP_CONF_TCP=0
 MAKE_MAC = MAKE_MAC_TSCH
 MODULES += os/net/app-layer/coap
 MODULES += os/services/orchestra os/lib/json
diff --git a/examples/platform-specific/jn516x/tsch/simple-sensor-network/rpl-border-router/project-conf.h b/examples/platform-specific/jn516x/tsch/simple-sensor-network/rpl-border-router/project-conf.h
index de5e4bdd6..52f716c41 100644
--- a/examples/platform-specific/jn516x/tsch/simple-sensor-network/rpl-border-router/project-conf.h
+++ b/examples/platform-specific/jn516x/tsch/simple-sensor-network/rpl-border-router/project-conf.h
@@ -35,14 +35,13 @@
 #define UIP_FALLBACK_INTERFACE rpl_interface
 #endif
 
+#define UIP_CONF_TCP 0
+
 /* Needed for slip-bridge */
-#undef SLIP_BRIDGE_CONF_NO_PUTCHAR
 #define SLIP_BRIDGE_CONF_NO_PUTCHAR 0
 
+#define UART_BAUD_RATE UART_RATE_230400
+
 #include "../../common-conf.h"
 
-#undef UART_BAUD_RATE
-#define UART_BAUD_RATE UART_RATE_230400
-
-
 #endif /* PROJECT_ROUTER_CONF_H_ */
diff --git a/examples/platform-specific/jn516x/tsch/tx-power-verification/node/Makefile b/examples/platform-specific/jn516x/tsch/tx-power-verification/node/Makefile
index 9a9cdc4f4..977210702 100644
--- a/examples/platform-specific/jn516x/tsch/tx-power-verification/node/Makefile
+++ b/examples/platform-specific/jn516x/tsch/tx-power-verification/node/Makefile
@@ -8,9 +8,6 @@ CONTIKI=../../../../../..
 PROJECTDIRS += .. ../../tools
 PROJECT_SOURCEFILES += rpl-tools.c
 
-CFLAGS += -DWITH_COAP
-CFLAGS += -DREST=coap_rest_implementation
-CFLAGS += -DUIP_CONF_TCP=0
 MAKE_MAC = MAKE_MAC_TSCH
 MODULES += os/net/app-layer/coap
 MODULES += os/services/orchestra os/lib/json
diff --git a/examples/platform-specific/jn516x/tsch/tx-power-verification/node/project-conf.h b/examples/platform-specific/jn516x/tsch/tx-power-verification/node/project-conf.h
index 77890c46e..0394b0ad5 100644
--- a/examples/platform-specific/jn516x/tsch/tx-power-verification/node/project-conf.h
+++ b/examples/platform-specific/jn516x/tsch/tx-power-verification/node/project-conf.h
@@ -34,9 +34,9 @@
 #ifndef __PROJECT_CONF_H__
 #define __PROJECT_CONF_H__
 
-#include "../../common-conf.h"
-
-#undef UART_BAUD_RATE
+#define UIP_CONF_TCP 0
 #define UART_BAUD_RATE UART_RATE_115200
 
+#include "../../common-conf.h"
+
 #endif /* __PROJECT_CONF_H__ */
diff --git a/examples/platform-specific/jn516x/tsch/tx-power-verification/rpl-border-router/Makefile b/examples/platform-specific/jn516x/tsch/tx-power-verification/rpl-border-router/Makefile
index 38c7a7ec2..c88fa5a2b 100644
--- a/examples/platform-specific/jn516x/tsch/tx-power-verification/rpl-border-router/Makefile
+++ b/examples/platform-specific/jn516x/tsch/tx-power-verification/rpl-border-router/Makefile
@@ -10,8 +10,6 @@ PROJECT_SOURCEFILES += slip-bridge.c slip.c
 PROJECTDIRS += .. ../../tools
 PROJECT_SOURCEFILES += rpl-tools.c
 
-CFLAGS += -DWITH_COAP
-CFLAGS += -DUIP_CONF_TCP=0
 MAKE_MAC = MAKE_MAC_TSCH
 MODULES += os/net/app-layer/coap
 MODULES += os/services/orchestra os/lib/json
diff --git a/examples/platform-specific/jn516x/tsch/tx-power-verification/rpl-border-router/project-conf.h b/examples/platform-specific/jn516x/tsch/tx-power-verification/rpl-border-router/project-conf.h
index 8a91daac0..c34c364e3 100644
--- a/examples/platform-specific/jn516x/tsch/tx-power-verification/rpl-border-router/project-conf.h
+++ b/examples/platform-specific/jn516x/tsch/tx-power-verification/rpl-border-router/project-conf.h
@@ -36,15 +36,13 @@
 #endif
 
 /* Needed for slip-bridge */
-#undef SLIP_BRIDGE_CONF_NO_PUTCHAR
 #define SLIP_BRIDGE_CONF_NO_PUTCHAR 0
 
+#define UIP_CONF_TCP 0
+#define QUEUEBUF_CONF_NUM 16
+
+#define TSCH_QUEUE_CONF_MAX_NEIGHBOR_QUEUES 8
+
 #include "../../common-conf.h"
 
-#undef QUEUEBUF_CONF_NUM
-#define QUEUEBUF_CONF_NUM 16
-
-#undef TSCH_QUEUE_CONF_MAX_NEIGHBOR_QUEUES
-#define TSCH_QUEUE_CONF_MAX_NEIGHBOR_QUEUES 8
-
 #endif /* PROJECT_ROUTER_CONF_H_ */
diff --git a/examples/platform-specific/jn516x/tsch/uart1-test-node/Makefile b/examples/platform-specific/jn516x/tsch/uart1-test-node/Makefile
index 22d1fdeb2..ca520969d 100644
--- a/examples/platform-specific/jn516x/tsch/uart1-test-node/Makefile
+++ b/examples/platform-specific/jn516x/tsch/uart1-test-node/Makefile
@@ -9,9 +9,6 @@ CONTIKI=../../../../..
 PROJECTDIRS += .. ../tools
 PROJECT_SOURCEFILES += rpl-tools.c
 
-CFLAGS += -DWITH_COAP
-CFLAGS += -DREST=coap_rest_implementation
-CFLAGS += -DUIP_CONF_TCP=0
 MAKE_MAC = MAKE_MAC_TSCH
 MODULES += os/net/app-layer/coap
 MODULES += os/services/orchestra os/lib/json
diff --git a/examples/platform-specific/jn516x/tsch/uart1-test-node/project-conf.h b/examples/platform-specific/jn516x/tsch/uart1-test-node/project-conf.h
index f72569a3c..373ea0f27 100644
--- a/examples/platform-specific/jn516x/tsch/uart1-test-node/project-conf.h
+++ b/examples/platform-specific/jn516x/tsch/uart1-test-node/project-conf.h
@@ -34,18 +34,16 @@
 #ifndef __PROJECT_CONF_H__
 #define __PROJECT_CONF_H__
 
-#include "../common-conf.h"
+#define UIP_CONF_TCP 0
 
-#undef UART_BAUD_RATE
 #define UART_BAUD_RATE UART_RATE_115200
 
-#undef UART1_BAUD_RATE
 #define UART1_BAUD_RATE UART_RATE_115200
  
-#undef UART1_CONF_TX_BUFFER_SIZE
 #define UART1_CONF_TX_BUFFER_SIZE 32
 
-#undef UART1_CONF_RX_BUFFER_SIZE
 #define UART1_CONF_RX_BUFFER_SIZE 32
 
+#include "../common-conf.h"
+
 #endif /* __PROJECT_CONF_H__ */
diff --git a/examples/platform-specific/nrf52dk/coap-demo/project-conf.h b/examples/platform-specific/nrf52dk/coap-demo/project-conf.h
index 2b097e8a8..3de6ff08e 100644
--- a/examples/platform-specific/nrf52dk/coap-demo/project-conf.h
+++ b/examples/platform-specific/nrf52dk/coap-demo/project-conf.h
@@ -46,33 +46,26 @@
 #define __PROJECT_ERBIUM_CONF_H__
 
 /* Disabling TCP on CoAP nodes. */
-#undef UIP_CONF_TCP
 #define UIP_CONF_TCP                   0
 
 /* Increase rpl-border-router IP-buffer when using more than 64. */
-#undef REST_MAX_CHUNK_SIZE
 #define REST_MAX_CHUNK_SIZE            48
 
 /* Estimate your header size, especially when using Proxy-Uri. */
 /*
-   #undef COAP_MAX_HEADER_SIZE
    #define COAP_MAX_HEADER_SIZE           70
  */
 
 /* Multiplies with chunk size, be aware of memory constraints. */
-#undef COAP_MAX_OPEN_TRANSACTIONS
 #define COAP_MAX_OPEN_TRANSACTIONS     4
 
 /* Must be <= open transactions, default is COAP_MAX_OPEN_TRANSACTIONS-1. */
 /*
-   #undef COAP_MAX_OBSERVERS
    #define COAP_MAX_OBSERVERS             2
  */
 
 /* Filtering .well-known/core per query can be disabled to save space. */
-#undef COAP_LINK_FORMAT_FILTERING
 #define COAP_LINK_FORMAT_FILTERING     0
-#undef COAP_PROXY_OPTION_PROCESSING
 #define COAP_PROXY_OPTION_PROCESSING   0
 
 /* Enable client-side support for COAP observe */
diff --git a/examples/platform-specific/zoul/at-test/project-conf.h b/examples/platform-specific/zoul/at-test/project-conf.h
index f2f918b48..3b756a01b 100644
--- a/examples/platform-specific/zoul/at-test/project-conf.h
+++ b/examples/platform-specific/zoul/at-test/project-conf.h
@@ -55,8 +55,6 @@
 
 /* Override serial-line defaults */
 #define SERIAL_LINE_CONF_BUFSIZE 128
-#undef IGNORE_CHAR
-#undef END
 #define IGNORE_CHAR(c) (c == 0x0d)
 #define END 0x0a
 
diff --git a/examples/platform-specific/zoul/orion/client/project-conf.h b/examples/platform-specific/zoul/orion/client/project-conf.h
index cbe867a14..ca2361f0a 100644
--- a/examples/platform-specific/zoul/orion/client/project-conf.h
+++ b/examples/platform-specific/zoul/orion/client/project-conf.h
@@ -35,7 +35,6 @@
 /* Use either the cc1200_driver for sub-1GHz, or cc2538_rf_driver (default)
  * for 2.4GHz built-in radio interface
  */
-#undef  NETSTACK_CONF_RADIO
 #define NETSTACK_CONF_RADIO              cc2538_rf_driver
 
 /* Alternate between ANTENNA_SW_SELECT_SUBGHZ or ANTENNA_SW_SELECT_2_4GHZ */
diff --git a/examples/platform-specific/zoul/orion/ip64-router/Makefile b/examples/platform-specific/zoul/orion/ip64-router/Makefile
index 4e184b119..8300617ca 100644
--- a/examples/platform-specific/zoul/orion/ip64-router/Makefile
+++ b/examples/platform-specific/zoul/orion/ip64-router/Makefile
@@ -6,7 +6,6 @@ CONTIKI = ../../../../..
 
 WITH_IP64 = 1
 
-DEFINES += UIP_CONF_TCP=1
 PROJECT_SOURCEFILES += httpd-simple.c
 
 include $(CONTIKI)/Makefile.include
diff --git a/examples/platform-specific/zoul/orion/ip64-router/project-conf.h b/examples/platform-specific/zoul/orion/ip64-router/project-conf.h
index 3918b646b..bbec833ad 100644
--- a/examples/platform-specific/zoul/orion/ip64-router/project-conf.h
+++ b/examples/platform-specific/zoul/orion/ip64-router/project-conf.h
@@ -55,7 +55,6 @@
 /* Use either the cc1200_driver for sub-1GHz, or cc2538_rf_driver (default)
  * for 2.4GHz built-in radio interface
  */
-#undef  NETSTACK_CONF_RADIO
 #define NETSTACK_CONF_RADIO         cc2538_rf_driver
 
 /* USe DHCP */
@@ -66,6 +65,7 @@
 #define UIP_CONF_RECEIVE_WINDOW     128
 #define WEBSERVER_CONF_CFS_CONNS    2
 #define UIP_CONF_BUFFER_SIZE        900
+#define UIP_CONF_TCP                  1
 #define UIP_CONF_TCP_MSS            128
 
 #endif /* PROJECT_CONF_H_ */
diff --git a/examples/sensniff/project-conf.h b/examples/sensniff/project-conf.h
index a68cfc933..f9097d465 100644
--- a/examples/sensniff/project-conf.h
+++ b/examples/sensniff/project-conf.h
@@ -33,7 +33,6 @@
 #define PROJECT_CONF_H_
 /*---------------------------------------------------------------------------*/
 /* Configure the sensniff_mac_driver for netstack.h */
-#undef NETSTACK_CONF_MAC
 #define NETSTACK_CONF_MAC      sensniff_mac_driver
 /*---------------------------------------------------------------------------*/
 /* Include platform-specific header */
diff --git a/os/dev/serial-line.c b/os/dev/serial-line.c
index 6c54331d8..80ff5510b 100644
--- a/os/dev/serial-line.c
+++ b/os/dev/serial-line.c
@@ -45,8 +45,13 @@
 #error Change SERIAL_LINE_CONF_BUFSIZE in contiki-conf.h.
 #endif
 
+#ifndef IGNORE_CHAR
 #define IGNORE_CHAR(c) (c == 0x0d)
+#endif
+
+#ifndef END
 #define END 0x0a
+#endif
 
 static struct ringbuf rxbuf;
 static uint8_t rxbuf_data[BUFSIZE];
diff --git a/os/net/app-layer/coap/coap-conf.h b/os/net/app-layer/coap/coap-conf.h
index 00d13d7c5..2aabc4be4 100644
--- a/os/net/app-layer/coap/coap-conf.h
+++ b/os/net/app-layer/coap/coap-conf.h
@@ -40,13 +40,18 @@
 #define ER_COAP_CONF_H_
 
 /* Features that can be disabled to achieve smaller memory footprint */
+#ifndef COAP_LINK_FORMAT_FILTERING
 #define COAP_LINK_FORMAT_FILTERING     0
+#endif /* COAP_LINK_FORMAT_FILTERING */
+
+#ifndef COAP_PROXY_OPTION_PROCESSING
 #define COAP_PROXY_OPTION_PROCESSING   0
+#endif /* COAP_PROXY_OPTION_PROCESSING */
 
 /* Listening port for the CoAP REST Engine */
 #ifndef COAP_SERVER_PORT
 #define COAP_SERVER_PORT               COAP_DEFAULT_PORT
-#endif
+#endif /* COAP_SERVER_PORT */
 
 /* The number of concurrent messages that can be stored for retransmission in the transaction layer. */
 #ifndef COAP_MAX_OPEN_TRANSACTIONS
@@ -69,6 +74,8 @@
 #endif /* COAP_MAX_OBSERVERS */
 
 /* Interval in notifies in which NON notifies are changed to CON notifies to check client. */
+#ifndef COAP_OBSERVE_REFRESH_INTERVAL
 #define COAP_OBSERVE_REFRESH_INTERVAL  20
+#endif /* COAP_OBSERVE_REFRESH_INTERVAL */
 
 #endif /* ER_COAP_CONF_H_ */
diff --git a/os/net/app-layer/httpd-ws/httpd-ws.h b/os/net/app-layer/httpd-ws/httpd-ws.h
index 9b6429979..a1164d94f 100644
--- a/os/net/app-layer/httpd-ws/httpd-ws.h
+++ b/os/net/app-layer/httpd-ws/httpd-ws.h
@@ -45,9 +45,9 @@
 
 #ifndef WEBSERVER_CONF_CFS_PATHLEN
 #define HTTPD_PATHLEN 80
-#else /* WEBSERVER_CONF_CFS_CONNS */
+#else /* WEBSERVER_CONF_CFS_PATHLEN */
 #define HTTPD_PATHLEN WEBSERVER_CONF_CFS_PATHLEN
-#endif /* WEBSERVER_CONF_CFS_CONNS */
+#endif /* WEBSERVER_CONF_CFS_PATHLEN */
 
 #ifndef WEBSERVER_CONF_INBUF_SIZE
 #define HTTPD_INBUF_SIZE (HTTPD_PATHLEN + 90)
diff --git a/tests/08-ipv6/code/receiver/project-conf.h b/tests/08-ipv6/code/receiver/project-conf.h
index 118578620..3ac43a91c 100644
--- a/tests/08-ipv6/code/receiver/project-conf.h
+++ b/tests/08-ipv6/code/receiver/project-conf.h
@@ -1,7 +1,5 @@
-#undef UIP_CONF_ND6_SEND_NS
 #define UIP_CONF_ND6_SEND_NS 1
 
 #ifdef BUFSIZE
-#undef UIP_CONF_BUFFER_SIZE
 #define UIP_CONF_BUFFER_SIZE BUFSIZE
 #endif /* BUFSIZE */
diff --git a/tests/08-ipv6/code/sender/project-conf.h b/tests/08-ipv6/code/sender/project-conf.h
index 118578620..3ac43a91c 100644
--- a/tests/08-ipv6/code/sender/project-conf.h
+++ b/tests/08-ipv6/code/sender/project-conf.h
@@ -1,7 +1,5 @@
-#undef UIP_CONF_ND6_SEND_NS
 #define UIP_CONF_ND6_SEND_NS 1
 
 #ifdef BUFSIZE
-#undef UIP_CONF_BUFFER_SIZE
 #define UIP_CONF_BUFFER_SIZE BUFSIZE
 #endif /* BUFSIZE */
diff --git a/tests/13-ieee802154/code-flush-nbr-queue/project-conf.h b/tests/13-ieee802154/code-flush-nbr-queue/project-conf.h
index 662bfcd88..52b95b95c 100644
--- a/tests/13-ieee802154/code-flush-nbr-queue/project-conf.h
+++ b/tests/13-ieee802154/code-flush-nbr-queue/project-conf.h
@@ -35,17 +35,13 @@
 #define UNIT_TEST_PRINT_FUNCTION test_print_report
 
 /* Set the minimum value of QUEUEBUF_CONF_NUM for the flush_nbr_queue test */
-#undef QUEUEBUF_CONF_NUM
 #define QUEUEBUF_CONF_NUM   1
 
 /* TSCH per-slot logging */
-#undef TSCH_LOG_CONF_PER_SLOT
 #define TSCH_LOG_CONF_PER_SLOT 1
 
-#undef TSCH_CONF_AUTOSTART
 #define TSCH_CONF_AUTOSTART 1
 
-#undef TSCH_CONF_WITH_SIXTOP
 #define TSCH_CONF_WITH_SIXTOP 1
 
 #if CONTIKI_TARGET_COOJA
diff --git a/tests/13-ieee802154/code/project-tsch-conf.h b/tests/13-ieee802154/code/project-tsch-conf.h
index bbe7c655b..868af4675 100644
--- a/tests/13-ieee802154/code/project-tsch-conf.h
+++ b/tests/13-ieee802154/code/project-tsch-conf.h
@@ -35,21 +35,15 @@
 #if WITH_SECURITY_ON
 #define TEST_CONFIG_TYPE SECURITY_ON
 
-#undef LLSEC802154_CONF_ENABLED
 #define LLSEC802154_CONF_ENABLED 1
 
 #elif WITH_ALL_ENABLED
 #define TEST_CONFIG_TYPE ALL_ENABLED
 
-#undef TSCH_PACKET_CONF_EACK_WITH_DEST_ADDR
 #define TSCH_PACKET_CONF_EACK_WITH_DEST_ADDR 1
-#undef TSCH_PACKET_CONF_EACK_WITH_SRC_ADDR
 #define TSCH_PACKET_CONF_EACK_WITH_SRC_ADDR 1
-#undef TSCH_PACKET_CONF_EB_WITH_TIMESLOT_TIMING
 #define TSCH_PACKET_CONF_EB_WITH_TIMESLOT_TIMING 1
-#undef TSCH_PACKET_CONF_EB_WITH_HOPPING_SEQUENCE
 #define TSCH_PACKET_CONF_EB_WITH_HOPPING_SEQUENCE 1
-#undef TSCH_PACKET_EB_WITH_SLOTFRAME_AND_LINK
 #define TSCH_PACKET_CONF_EB_WITH_SLOTFRAME_AND_LINK 1
 
 #endif
diff --git a/tests/14-rpl-lite/code/project-conf.h b/tests/14-rpl-lite/code/project-conf.h
index f4544bf5e..599ac1cbf 100644
--- a/tests/14-rpl-lite/code/project-conf.h
+++ b/tests/14-rpl-lite/code/project-conf.h
@@ -28,5 +28,4 @@
  */
 #define TCPIP_CONF_ANNOTATE_TRANSMISSIONS 1
 
-#undef RPL_CONF_MOP
 #define RPL_CONF_MOP RPL_MOP_NON_STORING
diff --git a/tests/16-6tisch/code/project-conf.h b/tests/16-6tisch/code/project-conf.h
index 0e857cbd6..3cd35f11d 100644
--- a/tests/16-6tisch/code/project-conf.h
+++ b/tests/16-6tisch/code/project-conf.h
@@ -37,36 +37,27 @@
 //#error "This file is intended to be used for Cooja mote."
 #endif /* CONTIKI_TARGET_COOJA */
 
-#undef SIXTOP_CONF_MAX_SCHEDULING_FUNCTIONS
 #define SIXTOP_CONF_MAX_SCHEDULING_FUNCTIONS 2
 
-#undef SIXTOP_CONF_MAX_TRANSACTIONS
 #define SIXTOP_CONF_MAX_TRANSACTIONS      2
 
-#undef SIXP_CONF_WITH_PAYLOAD_TERMINATION_IE
 #define SIXP_CONF_WITH_PAYLOAD_TERMINATION_IE 1
 
-#undef NBR_TABLE_CONF_MAX_NEIGHBORS
 #define NBR_TABLE_CONF_MAX_NEIGHBORS         2
 
 #define UNIT_TEST_PRINT_FUNCTION test_print_report
 
-#undef TSCH_CONF_WITH_SIXTOP
 #define TSCH_CONF_WITH_SIXTOP 1
 
-#undef TSCH_LOG_CONF_PER_SLOT
 #define TSCH_LOG_CONF_PER_SLOT 1
 
 #define LOG_CONF_LEVEL_6TOP LOG_LEVEL_DBG
 
-#undef TSCH_CONF_AUTOSTART
 #define TSCH_CONF_AUTOSTART 0
 
-#undef IEEE802154_CONF_PANID
 #define IEEE802154_CONF_PANID 0xabcd
 
 /* Custom MAC layer */
-#undef NETSTACK_CONF_MAC
 #define NETSTACK_CONF_MAC        test_mac_driver
 
 #endif /* __PROJECT_CONF_H__ */