diff --git a/mm/slob.c b/mm/slob.c
index a886e83..de5d556 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -484,7 +484,8 @@
 {
 	struct slob_page *sp;
 
-	if (unlikely(ZERO_OR_NULL_PTR(block)))
+	BUG_ON(!block);
+	if (unlikely(block == ZERO_SIZE_PTR))
 		return 0;
 
 	sp = (struct slob_page *)virt_to_page(block);