diff --git a/core/net/mac/contikimac.c b/core/net/mac/contikimac.c
index ef33cf7e8..7027c5685 100644
--- a/core/net/mac/contikimac.c
+++ b/core/net/mac/contikimac.c
@@ -215,7 +215,6 @@ static volatile uint8_t contikimac_keep_radio_on = 0;
 static volatile unsigned char we_are_sending = 0;
 static volatile unsigned char radio_is_on = 0;
 
-#undef DEBUG
 #define DEBUG 0
 #if DEBUG
 #include <stdio.h>
diff --git a/core/net/rime/collect.c b/core/net/rime/collect.c
index cc99981ee..6f16b4b4d 100644
--- a/core/net/rime/collect.c
+++ b/core/net/rime/collect.c
@@ -193,7 +193,6 @@ struct {
 
 /* Debug definition: draw routing tree in Cooja. */
 #define DRAW_TREE 0
-#undef DEBUG
 #define DEBUG 0
 #if DEBUG
 #include <stdio.h>
diff --git a/core/net/uiplib.c b/core/net/uiplib.c
index 128111b98..e01f7d672 100644
--- a/core/net/uiplib.c
+++ b/core/net/uiplib.c
@@ -37,7 +37,6 @@
 #include "net/uiplib.h"
 #include <string.h>
 
-#undef DEBUG
 #define DEBUG DEBUG_NONE
 #include "net/uip-debug.h"