diff --git a/lib/zlib.js b/lib/zlib.js
index 5266c1cfe4a2b1..19405263c92896 100644
--- a/lib/zlib.js
+++ b/lib/zlib.js
@@ -92,9 +92,7 @@ const codes = {
   Z_VERSION_ERROR: constants.Z_VERSION_ERROR
 };
 
-const ckeys = ObjectKeys(codes);
-for (let ck = 0; ck < ckeys.length; ck++) {
-  const ckey = ckeys[ck];
+for (const ckey of ObjectKeys(codes)) {
   codes[codes[ckey]] = ckey;
 }
 
@@ -912,9 +910,7 @@ ObjectDefineProperties(module.exports, {
 
 // These should be considered deprecated
 // expose all the zlib constants
-const bkeys = ObjectKeys(constants);
-for (let bk = 0; bk < bkeys.length; bk++) {
-  const bkey = bkeys[bk];
+for (const bkey of ObjectKeys(constants)) {
   if (bkey.startsWith('BROTLI')) continue;
   ObjectDefineProperty(module.exports, bkey, {
     enumerable: false, value: constants[bkey], writable: false