diff --git a/src/gui_gtk_x11.c b/src/gui_gtk_x11.c
index 518edaf..d4a8b93 100644
--- a/src/gui_gtk_x11.c
+++ b/src/gui_gtk_x11.c
@@ -2065,7 +2065,7 @@
 #endif
 #define DT_X11     1
 #define DT_WAYLAND 2
-    static display_type;
+    static int display_type;
     if (!display_type)
 	display_type = gui_mch_get_display() ? DT_X11 : DT_WAYLAND;
 #endif