diff --git a/tree.go b/tree.go
index 8f92c62d..160775ed 100644
--- a/tree.go
+++ b/tree.go
@@ -1180,14 +1180,14 @@ func (leaf *LeafNode) Commit() *Point {
 			if !bytes.Equal(oldValue, leaf.values[i]) {
 				if i < 128 {
 					if c1 == nil {
-						c1, old1 = leaf.getOldCn(byte(i))
+						c1, old1 = leaf.getOldCn(i)
 					}
-					leaf.updateCn(byte(i), oldValue, c1)
+					leaf.updateCn(i, oldValue, c1)
 				} else {
 					if c2 == nil {
-						c2, old2 = leaf.getOldCn(byte(i))
+						c2, old2 = leaf.getOldCn(i)
 					}
-					leaf.updateCn(byte(i), oldValue, c2)
+					leaf.updateCn(i, oldValue, c2)
 				}
 			}
 		}