diff -uprN gtk-sharp-2.12.41.old/gdk/glue/windowmanager.c gtk-sharp-2.12.41/gdk/glue/windowmanager.c
--- gtk-sharp-2.12.41.old/gdk/glue/windowmanager.c	2016-10-04 20:08:41.000000000 +0300
+++ gtk-sharp-2.12.41/gdk/glue/windowmanager.c	2018-02-07 16:08:50.206366227 +0300
@@ -110,7 +110,7 @@ gtksharp_get_gdk_net_client_list (int *c
 	list = g_malloc (*count * sizeof (gpointer));
 	/* Put all of the windows into a GList to return */
 	for (i = 0; i < *count; i ++) {
-		list [i] = data [i];
+		list [i] = (gpointer)(data [i]);
 		g_message ("WinID: %d", list [i]);
 	}