diff --git a/drivers/video/fbcmap.c b/drivers/video/fbcmap.c
index 008212069ac6..520276154d7a 100644
--- a/drivers/video/fbcmap.c
+++ b/drivers/video/fbcmap.c
@@ -196,7 +196,7 @@ int fb_cmap_to_user(const struct fb_cmap *from, struct fb_cmap_user *to)
 	int tooff = 0, fromoff = 0;
 	int size;
 
-	if (!to || !from)
+	if (!to || !from || (int)(to->start) < 0)
 		return -EINVAL;
 
 	if (to->start > from->start)