diff --git a/src/util-strings.c b/src/util-strings.c
index d0a3fa0..249604b 100644
--- a/src/util-strings.c
+++ b/src/util-strings.c
@@ -23,6 +23,7 @@
  */
 
 #include "config.h"
+#define _GNU_SOURCE
 
 #include "util-strings.h"
 
diff --git a/src/util-strings.h b/src/util-strings.h
index 89d42c0..47306b8 100644
--- a/src/util-strings.h
+++ b/src/util-strings.h
@@ -24,9 +24,6 @@
 
 #pragma once
 
-#include "config.h"
-#define _GNU_SOURCE
-
 #include <assert.h>
 #include <ctype.h>
 #include <errno.h>
diff --git a/src/xf86libinput.c b/src/xf86libinput.c
index ad059be..86b9cb9 100644
--- a/src/xf86libinput.c
+++ b/src/xf86libinput.c
@@ -24,6 +24,7 @@
  */
 
 #include "config.h"
+#define _GNU_SOURCE
 
 #include <errno.h>
 #include <fcntl.h>