diff --git a/mm/slob.c b/mm/slob.c
index b90091c..2e9236e 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -334,7 +334,7 @@
 }
 EXPORT_SYMBOL(kmem_cache_shrink);
 
-int kmem_ptr_validate(struct kmem_cache *a, void *b)
+int kmem_ptr_validate(struct kmem_cache *a, const void *b)
 {
 	return 0;
 }