diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
index 6b453e72..9705af14 100644
--- a/CONTRIBUTORS.md
+++ b/CONTRIBUTORS.md
@@ -183,6 +183,7 @@ video tutorials.
  - Jon Morton
  - Pierre Moulon
  - Martins Mozeiko
+ - Tomáš Mráz
  - Pascal Muetschard
  - James Murphy
  - Julian Møller
diff --git a/src/wl_window.c b/src/wl_window.c
index 468360fe..7d0a8309 100644
--- a/src/wl_window.c
+++ b/src/wl_window.c
@@ -24,7 +24,9 @@
 //
 //========================================================================
 
-#define _GNU_SOURCE
+#if !defined(_GNU_SOURCE)
+ #define _GNU_SOURCE
+#endif
 
 #include "internal.h"