diff --git a/core/net/tcpip.c b/core/net/tcpip.c
index 12b95ce9e..a4f86fe44 100644
--- a/core/net/tcpip.c
+++ b/core/net/tcpip.c
@@ -29,7 +29,7 @@
  * This file is part of the Contiki operating system.
  *
  *
- * $Id: tcpip.c,v 1.18 2009/02/20 07:59:36 julienabeille Exp $
+ * $Id: tcpip.c,v 1.19 2009/02/20 21:21:56 adamdunkels Exp $
  */
 /**
  * \file
@@ -107,14 +107,42 @@ enum {
 
 /* Called on IP packet output. */
 #if UIP_CONF_IPV6
-u8_t (* tcpip_output)(uip_lladdr_t *);
-#else
-static u8_t dummy_tcpip_output_function(void)
+
+static u8_t (* outputfunc)(uip_lladdr_t *a);
+
+u8_t
+tcpip_output(uip_lladdr_t *a)
 {
-  UIP_LOG("dummy_tcpip_output_function: Use tcpip_set_outputfunc() to replace this dummy");
+  if(outputfunc != NULL) {
+    return outputfunc(a);
+  }
+  UIP_LOG("tcpip_output: Use tcpip_set_outputfunc() to set an output function");
   return 0;
 }
-u8_t (* tcpip_output)(void) = dummy_tcpip_output_function;
+
+void
+tcpip_set_outputfunc(u8_t (*f)(uip_lladdr_t *))
+{
+  outputfunc = f;
+}
+#else
+
+static u8_t (* outputfunc)(void);
+u8_t
+tcpip_output(void)
+{
+  if(outputfunc != NULL) {
+    return outputfunc();
+  }
+  UIP_LOG("tcpip_output: Use tcpip_set_outputfunc() to set an output function");
+  return 0;
+}
+
+void
+tcpip_set_outputfunc(u8_t (*f)(void))
+{
+  outputfunc = f;
+}
 #endif
 
 #if UIP_CONF_IP_FORWARD
@@ -685,7 +713,7 @@ PROCESS_THREAD(tcpip_process, ev, data)
    s.p = PROCESS_CURRENT();
  }
 #endif
-  
+
   tcpip_event = process_alloc_event();
   etimer_set(&periodic, CLOCK_SECOND/2);
 
diff --git a/core/net/tcpip.h b/core/net/tcpip.h
index afe451f62..2246682ec 100644
--- a/core/net/tcpip.h
+++ b/core/net/tcpip.h
@@ -62,7 +62,7 @@
  *
  * Author: Adam Dunkels <adam@sics.se>
  *
- * $Id: tcpip.h,v 1.12 2008/10/14 09:40:56 julienabeille Exp $
+ * $Id: tcpip.h,v 1.13 2009/02/20 21:21:57 adamdunkels Exp $
  */
 #ifndef __TCPIP_H__
 #define __TCPIP_H__
@@ -288,11 +288,11 @@ CCIF void tcpip_poll_udp(struct uip_udp_conn *conn);
  *
  * This function just registers a process to be polled when
  * an ICMPv6 message is received.
- * If no application registers, some ICMPv6 packets will be 
+ * If no application registers, some ICMPv6 packets will be
  * processed by the "kernel" as usual (NS, NA, RS, RA, Echo request),
  * others will be dropped.
  * If an appplication registers here, it will be polled with a
- * process_post_synch everytime an ICMPv6 packet is received. 
+ * process_post_synch everytime an ICMPv6 packet is received.
  */
 u8_t icmp6_new(void *appstate);
 
@@ -333,9 +333,11 @@ CCIF void tcpip_input(void);
  * The eventual parameter is the MAC address of the destination.
  */
 #if UIP_CONF_IPV6
-extern u8_t (* tcpip_output)(uip_lladdr_t *);
+u8_t tcpip_output(uip_lladdr_t *);
+void tcpip_set_outputfunc(u8_t (* f)(uip_lladdr_t *));
 #else
-extern u8_t (* tcpip_output)(void);
+void tcpip_set_outputfunc(u8_t (* f)(void));
+u8_t tcpip_output(void);
 #endif
 
 /**
@@ -355,7 +357,7 @@ extern unsigned char tcpip_do_forwarding;
  */
 extern unsigned char tcpip_is_forwarding;
 
-#define tcpip_set_outputfunc(outputfunc) tcpip_output        = (outputfunc)
+
 #define tcpip_set_forwarding(forwarding) tcpip_do_forwarding = (forwarding)
 
 /** @} */