diff --git a/Makefile b/Makefile
index 28b7a636..06388cb9 100644
--- a/Makefile
+++ b/Makefile
@@ -16,6 +16,10 @@ CFLAGS += -I/usr/pkg/include
 LDFLAGS += -Wl,-rpath,/usr/local/lib -Wl,-rpath,/usr/pkg/lib
 endif
 
+ifeq ($(UNAME),Linux)
+CFLAGS += -D_GNU_SOURCE
+endif
+
 ifeq ($(DEBUG),1)
 # Extended debugging flags, macros shall be available in gcc
 CFLAGS += -gdwarf-2
diff --git a/src/layout.c b/src/layout.c
index a3b87f17..48fcaf36 100644
--- a/src/layout.c
+++ b/src/layout.c
@@ -10,7 +10,6 @@
  * layout.c: Functions handling layout/drawing of window decorations
  *
  */
-#define _GNU_SOURCE
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
diff --git a/src/mainx.c b/src/mainx.c
index 70a0f819..b8a8da19 100644
--- a/src/mainx.c
+++ b/src/mainx.c
@@ -8,7 +8,6 @@
  * See file LICENSE for license information.
  *
  */
-#define _GNU_SOURCE
 #include <stdio.h>
 #include <assert.h>
 #include <stdlib.h>