diff --git a/lib/bcoin/script.js b/lib/bcoin/script.js
index 38d0c3dc..84791477 100644
--- a/lib/bcoin/script.js
+++ b/lib/bcoin/script.js
@@ -1370,7 +1370,7 @@ Script.createWitnessProgram = function createWitnessProgram(version, data) {
   return new Script([version === 0 ? 0 : version + 0x50, data]);
 };
 
-Script.prototype.createCommitment = function createCommitment(hash) {
+Script.createCommitment = function createCommitment(hash) {
   return new Script([
     opcodes.OP_RETURN,
     Buffer.concat([new Buffer([0xaa, 0x21, 0xa9, 0xed]), hash])