diff --git a/grub-core/normal/completion.c b/grub-core/normal/completion.c
index 596102848..c07100a8d 100644
--- a/grub-core/normal/completion.c
+++ b/grub-core/normal/completion.c
@@ -284,7 +284,8 @@ complete_file (void)
 
       /* Cut away the filename part.  */
       dirfile = grub_strrchr (dir, '/');
-      dirfile[1] = '\0';
+      if (dirfile)
+	dirfile[1] = '\0';
 
       /* Iterate the directory.  */
       (fs->fs_dir) (dev, dir, iterate_dir, NULL);