diff --git a/os/net/app-layer/coap/coap.h b/os/net/app-layer/coap/coap.h
index 9d88886af..616f67d5c 100644
--- a/os/net/app-layer/coap/coap.h
+++ b/os/net/app-layer/coap/coap.h
@@ -46,7 +46,7 @@
 
 /* sanity check for configured values */
 #define COAP_MAX_PACKET_SIZE  (COAP_MAX_HEADER_SIZE + REST_MAX_CHUNK_SIZE)
-#if COAP_MAX_PACKET_SIZE > (UIP_BUFSIZE - UIP_IPH_LEN - UIP_UDPH_LEN)
+#if COAP_MAX_PACKET_SIZE > (UIP_BUFSIZE - UIP_LLH_LEN - UIP_IPH_LEN - UIP_UDPH_LEN)
 #error "UIP_CONF_BUFFER_SIZE too small for REST_MAX_CHUNK_SIZE"
 #endif
 
diff --git a/os/net/rpl-classic/rpl-ext-header.c b/os/net/rpl-classic/rpl-ext-header.c
index 0c1f8076a..a0fdb0eb4 100644
--- a/os/net/rpl-classic/rpl-ext-header.c
+++ b/os/net/rpl-classic/rpl-ext-header.c
@@ -408,7 +408,7 @@ insert_srh_header(void)
       path_len, cmpri, cmpre, ext_len, padding);
 
   /* Check if there is enough space to store the extension header */
-  if(uip_len + ext_len > UIP_BUFSIZE) {
+  if(uip_len + ext_len > UIP_BUFSIZE - UIP_LLH_LEN) {
     PRINTF("RPL: Packet too long: impossible to add source routing header (%u bytes)\n", ext_len);
     return 0;
   }
@@ -553,7 +553,7 @@ insert_hbh_header(const rpl_instance_t *instance)
 
   /* Insert hop-by-hop header */
   PRINTF("RPL: Creating hop-by-hop option\n");
-  if(uip_len + RPL_HOP_BY_HOP_LEN > UIP_BUFSIZE) {
+  if(uip_len + RPL_HOP_BY_HOP_LEN > UIP_BUFSIZE - UIP_LLH_LEN) {
     PRINTF("RPL: Packet too long: impossible to add hop-by-hop option\n");
     uip_ext_len = last_uip_ext_len;
     return 0;
diff --git a/os/net/rpl-lite/rpl-ext-header.c b/os/net/rpl-lite/rpl-ext-header.c
index e71e6c1f6..96455e85c 100644
--- a/os/net/rpl-lite/rpl-ext-header.c
+++ b/os/net/rpl-lite/rpl-ext-header.c
@@ -302,7 +302,7 @@ insert_srh_header(void)
       path_len, cmpri, cmpre, ext_len, padding);
 
   /* Check if there is enough space to store the extension header */
-  if(uip_len + ext_len > UIP_BUFSIZE) {
+  if(uip_len + ext_len > UIP_BUFSIZE - UIP_LLH_LEN) {
     LOG_ERR("packet too long: impossible to add source routing header (%u bytes)\n", ext_len);
     return 0;
   }
@@ -464,7 +464,7 @@ insert_hbh_header(void)
 
   /* Insert hop-by-hop header */
   LOG_INFO("creating hop-by-hop option\n");
-  if(uip_len + RPL_HOP_BY_HOP_LEN > UIP_BUFSIZE) {
+  if(uip_len + RPL_HOP_BY_HOP_LEN > UIP_BUFSIZE - UIP_LLH_LEN) {
     LOG_ERR("packet too long: impossible to add hop-by-hop option\n");
     uip_ext_len = last_uip_ext_len;
     return 0;
diff --git a/os/services/ip64/ip64-dhcpc.c b/os/services/ip64/ip64-dhcpc.c
index 81d97490d..8e8e286f8 100644
--- a/os/services/ip64/ip64-dhcpc.c
+++ b/os/services/ip64/ip64-dhcpc.c
@@ -61,7 +61,7 @@ struct dhcp_msg {
   uint8_t options[312];
 };
 
-#if (UIP_BUFSIZE - UIP_UDPIP_HLEN) < 548
+#if (UIP_BUFSIZE - UIP_LLH_LEN - UIP_UDPIP_HLEN) < 548
 #error UIP_CONF_BUFFER_SIZE may be too small to accomodate DHCPv4 packets
 #error Increase UIP_CONF_BUFFER_SIZE in your project-conf.h, or contiki-conf.h
 #error A good size is 600 bytes