diff --git a/auditing.go b/auditing.go
index 69158bc..a5768ec 100644
--- a/auditing.go
+++ b/auditing.go
@@ -184,3 +184,7 @@ func (builder *MerkleTreeBuilder) CalculateRoot() ct.MerkleTreeNode {
 	}
 	return hash
 }
+
+func (builder *MerkleTreeBuilder) GetNumLeaves() uint64 {
+	return builder.numLeaves
+}