diff --git a/tree.go b/tree.go
index cb568d2b..c76fed3b 100644
--- a/tree.go
+++ b/tree.go
@@ -40,12 +40,6 @@ type (
 	NodeResolverFn func([]byte) ([]byte, error)
 )
 
-// Committer represents an object that is able to create the
-// commitment to a polynomial.
-type Committer interface {
-	CommitToPoly([]Fr, int) Point
-}
-
 type keylist [][]byte
 
 func (kl keylist) Len() int {
@@ -932,7 +926,6 @@ func (n *LeafNode) getOldCn(index byte) (*Point, *Fr) {
 func (n *LeafNode) updateC(stem []byte, index byte, c *Point, oldc *Fr) {
 	var (
 		newc Fr
-		diff Point
 		poly [256]Fr
 	)
 
@@ -943,12 +936,10 @@ func (n *LeafNode) updateC(stem []byte, index byte, c *Point, oldc *Fr) {
 	if n.commitment == nil {
 		poly[0].SetUint64(1)
 		StemFromBytes(&poly[1], stem)
-		comm := cfg.conf.Commit(poly[:])
-		n.commitment = &comm
+		n.commitment = cfg.CommitToPoly(poly[:], 0)
 		return
 	}
-	diff = cfg.conf.Commit(poly[:])
-	n.commitment.Add(n.commitment, &diff)
+	n.commitment.Add(n.commitment, cfg.CommitToPoly(poly[:], 0))
 }
 
 func (n *LeafNode) updateCn(index byte, oldValue []byte, c *Point) {