diff --git a/src/gui.c b/src/gui.c
index 63625bf..f774750 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -4933,7 +4933,7 @@
 }
 
 /*
- * Find window where the mouse pointer "y" coordinate is in.
+ * Find window where the mouse pointer "x" / "y" coordinate is in.
  */
     static win_T *
 xy2win(int x UNUSED, int y UNUSED)
@@ -4948,6 +4948,8 @@
     if (row < 0 || col < 0)		/* before first window */
 	return NULL;
     wp = mouse_find_win(&row, &col);
+    if (wp == NULL)
+	return NULL;
 # ifdef FEAT_MOUSESHAPE
     if (State == HITRETURN || State == ASKMORE)
     {