diff --git a/src/Makefile.am b/src/Makefile.am
index 88bc76de0..a86fe9113 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -16,6 +16,7 @@ AM_CPPFLAGS = \
 	-DCOGL_ENABLE_MUTTER_API					\
 	-DCLUTTER_DISABLE_DEPRECATION_WARNINGS				\
 	-DCOGL_DISABLE_DEPRECATION_WARNINGS				\
+	-D_GNU_SOURCE							\
 	$(MUTTER_CFLAGS)						\
 	$(MUTTER_NATIVE_BACKEND_CFLAGS)					\
 	-I$(builddir)							\
@@ -645,7 +646,7 @@ Meta_@LIBMUTTER_API_VERSION@_gir_INCLUDES =	\
 	xfixes-4.0				\
 	$(NULL)
 Meta_@LIBMUTTER_API_VERSION@_gir_EXPORT_PACKAGES = libmutter-$(LIBMUTTER_API_VERSION)
-Meta_@LIBMUTTER_API_VERSION@_gir_CFLAGS = $(AM_CPPFLAGS)
+Meta_@LIBMUTTER_API_VERSION@_gir_CFLAGS = $(AM_CPPFLAGS) -U_GNU_SOURCE
 Meta_@LIBMUTTER_API_VERSION@_gir_LIBS = libmutter-$(LIBMUTTER_API_VERSION).la
 Meta_@LIBMUTTER_API_VERSION@_gir_FILES =			\
 	$(libmutterinclude_base_headers)			\
diff --git a/src/backends/meta-remote-desktop.c b/src/backends/meta-remote-desktop.c
index cd32fae0f..d741dccd8 100644
--- a/src/backends/meta-remote-desktop.c
+++ b/src/backends/meta-remote-desktop.c
@@ -20,8 +20,6 @@
  *
  */
 
-#define _GNU_SOURCE
-
 #include "config.h"
 
 #include "backends/meta-remote-desktop.h"
diff --git a/src/wayland/meta-wayland-tablet-manager.c b/src/wayland/meta-wayland-tablet-manager.c
index 62faf884d..018d81940 100644
--- a/src/wayland/meta-wayland-tablet-manager.c
+++ b/src/wayland/meta-wayland-tablet-manager.c
@@ -21,8 +21,6 @@
  * Author: Carlos Garnacho <carlosg@gnome.org>
  */
 
-#define _GNU_SOURCE
-
 #include "config.h"
 
 #include <glib.h>
diff --git a/src/wayland/meta-wayland-tablet-pad-group.c b/src/wayland/meta-wayland-tablet-pad-group.c
index 04acbb8d4..93d5eb3f2 100644
--- a/src/wayland/meta-wayland-tablet-pad-group.c
+++ b/src/wayland/meta-wayland-tablet-pad-group.c
@@ -21,8 +21,6 @@
  * Author: Carlos Garnacho <carlosg@gnome.org>
  */
 
-#define _GNU_SOURCE
-
 #include "config.h"
 
 #include <wayland-server.h>
diff --git a/src/wayland/meta-wayland-tablet-pad-ring.c b/src/wayland/meta-wayland-tablet-pad-ring.c
index 7a6876c06..a89f5dd94 100644
--- a/src/wayland/meta-wayland-tablet-pad-ring.c
+++ b/src/wayland/meta-wayland-tablet-pad-ring.c
@@ -21,8 +21,6 @@
  * Author: Carlos Garnacho <carlosg@gnome.org>
  */
 
-#define _GNU_SOURCE
-
 #include "config.h"
 
 #include "wayland/meta-wayland-tablet-pad-ring.h"
diff --git a/src/wayland/meta-wayland-tablet-pad-strip.c b/src/wayland/meta-wayland-tablet-pad-strip.c
index 6d7b1e254..6f6c20d8d 100644
--- a/src/wayland/meta-wayland-tablet-pad-strip.c
+++ b/src/wayland/meta-wayland-tablet-pad-strip.c
@@ -21,8 +21,6 @@
  * Author: Carlos Garnacho <carlosg@gnome.org>
  */
 
-#define _GNU_SOURCE
-
 #include "config.h"
 
 #include "wayland/meta-wayland-tablet-pad-strip.h"
diff --git a/src/wayland/meta-wayland-tablet-pad.c b/src/wayland/meta-wayland-tablet-pad.c
index e05923522..7c7d880b6 100644
--- a/src/wayland/meta-wayland-tablet-pad.c
+++ b/src/wayland/meta-wayland-tablet-pad.c
@@ -21,8 +21,6 @@
  * Author: Carlos Garnacho <carlosg@gnome.org>
  */
 
-#define _GNU_SOURCE
-
 #include "config.h"
 
 #include <glib.h>
diff --git a/src/wayland/meta-wayland-tablet-seat.c b/src/wayland/meta-wayland-tablet-seat.c
index bee1a453b..dd35724c4 100644
--- a/src/wayland/meta-wayland-tablet-seat.c
+++ b/src/wayland/meta-wayland-tablet-seat.c
@@ -21,8 +21,6 @@
  * Author: Carlos Garnacho <carlosg@gnome.org>
  */
 
-#define _GNU_SOURCE
-
 #include "config.h"
 
 #include <glib.h>
diff --git a/src/wayland/meta-wayland-tablet-tool.c b/src/wayland/meta-wayland-tablet-tool.c
index a3b87ffc2..222b46633 100644
--- a/src/wayland/meta-wayland-tablet-tool.c
+++ b/src/wayland/meta-wayland-tablet-tool.c
@@ -21,8 +21,6 @@
  * Author: Carlos Garnacho <carlosg@gnome.org>
  */
 
-#define _GNU_SOURCE
-
 #include "config.h"
 
 #include "wayland/meta-wayland-tablet-tool.h"
diff --git a/src/wayland/meta-wayland-tablet.c b/src/wayland/meta-wayland-tablet.c
index dd1d6f600..763f804b2 100644
--- a/src/wayland/meta-wayland-tablet.c
+++ b/src/wayland/meta-wayland-tablet.c
@@ -21,8 +21,6 @@
  * Author: Carlos Garnacho <carlosg@gnome.org>
  */
 
-#define _GNU_SOURCE
-
 #include "config.h"
 
 #include "wayland/meta-wayland-tablet.h"