diff --git a/src/freewins/freewins.h b/src/freewins/freewins.h
index f5d3640ba4f91288d8b8b029011d2cd63f1d41b7..81996934666b02f3066c9dbfb27ded7e17f9dad1 100644
--- a/src/freewins/freewins.h
+++ b/src/freewins/freewins.h
@@ -338,7 +338,7 @@ typedef struct _FWWindow
 
 } FWWindow;
 
-int displayPrivateIndex;
+extern int displayPrivateIndex;
 
 /* ------ Forward Declarations --------------------------------------------*/