diff --git a/grub-core/fs/cbfs.c b/grub-core/fs/cbfs.c
index 5fc9c0147..0842701a6 100644
--- a/grub-core/fs/cbfs.c
+++ b/grub-core/fs/cbfs.c
@@ -352,7 +352,7 @@ init_cbfsdisk (void)
      reading ROMs through controller directly.
    */
   if (ptr < 0xff000000
-      || 0xffffffff - ptr < sizeof (*head) + 0x10
+      || 0xffffffff - ptr < (grub_uint32_t) sizeof (*head) + 0xf
       || !validate_head (head))
     return;