diff --git a/src/config.in b/src/config.in
index 94e9a44b3b7bebf75f9077e4e6b641ed033e905b..e09e1289b8dd19a57b8661685d65dcd139fe2b4b 100644
--- a/src/config.in
+++ b/src/config.in
@@ -69,6 +69,7 @@ and this notice must be preserved on all copies.  */
 
 /* If we're using any sort of window system, define some consequences.  */
 #ifdef HAVE_X_WINDOWS
+#define HAVE_WINDOW_SYSTEM
 #define MULTI_KBOARD
 #define HAVE_FACES
 #define HAVE_MOUSE