diff --git a/src/popupwin.c b/src/popupwin.c
index b089552..1122f48 100644
--- a/src/popupwin.c
+++ b/src/popupwin.c
@@ -3331,8 +3331,12 @@
     char_u	*cells;
     int		row, col;
 
-    if (wp->w_popup_mask == NULL)
+    if (wp->w_popup_mask == NULL || width == 0 || height == 0)
+    {
+	vim_free(wp->w_popup_mask_cells);
+	wp->w_popup_mask_cells = NULL;
 	return;
+    }
     if (wp->w_popup_mask_cells != NULL
 	    && wp->w_popup_mask_height == height
 	    && wp->w_popup_mask_width == width)