--- a/input-pad/window-gtk.c
+++ b/input-pad/window-gtk.c
@@ -5462,7 +5462,7 @@
 
     app = INPUT_PAD_GTK_APPLICATION (window_data);
 
-    g_return_if_fail (app->window != NULL);
+    g_return_val_if_fail (app->window != NULL, 0);
 
     return gtk_widget_get_visible (GTK_WIDGET (app->window));
 }
@@ -5661,8 +5661,9 @@
 {
     InputPadGtkApplication *app;
 
-    g_return_if_fail (window_data != NULL &&
-                      INPUT_PAD_IS_GTK_APPLICATION (window_data));
+    g_return_val_if_fail (window_data != NULL &&
+                          INPUT_PAD_IS_GTK_APPLICATION (window_data),
+                          -1);
 
     app = INPUT_PAD_GTK_APPLICATION (window_data);