diff --git a/src/gui/sdlmain.cpp b/src/gui/sdlmain.cpp
index 56edcc2d..7aeda676 100644
--- a/src/gui/sdlmain.cpp
+++ b/src/gui/sdlmain.cpp
@@ -15,6 +15,9 @@
  *  along with this program; if not, write to the Free Software
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
 
 #include <string.h>
 #include <stdio.h>