diff --git a/lib/kref.c b/lib/kref.c
index 9ecd6e8..e143fd8 100644
--- a/lib/kref.c
+++ b/lib/kref.c
@@ -64,6 +64,8 @@ int kref_put(struct kref *kref, void (*release)(struct kref *kref))
 	WARN_ON(release == NULL);
 	WARN_ON(release == (void (*)(struct kref *))kfree);
 
+	WARN_ON((atomic_read(&kref->refcount) & 0xffffffff) == 0x6b6b6b6b);
+
 	if (atomic_dec_and_test(&kref->refcount)) {
 		release(kref);
 		return 1;