diff --git a/src/lindbergh/graphics.c b/src/lindbergh/graphics.c
index 104da34..383e5e0 100644
--- a/src/lindbergh/graphics.c
+++ b/src/lindbergh/graphics.c
@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
 #include <GL/freeglut.h>
 #include <GL/glx.h>
 #include <X11/extensions/xf86vmode.h>