diff --git a/bolt.go b/bolt.go
index 8e761e4..47004a3 100755
--- a/bolt.go
+++ b/bolt.go
@@ -61,7 +61,7 @@ func (b *Bolt) Set(key string, value []byte, ns ...string) error {
 			return err
 		}
 		if value == nil {
-			return bkt.Delete(key)
+			return bkt.Delete([]byte(key))
 		}
 		return bkt.Put([]byte(key), value)
 	})