diff --git a/lib/zlib.js b/lib/zlib.js
index 509f83731e9116..1a00ea59b484a6 100644
--- a/lib/zlib.js
+++ b/lib/zlib.js
@@ -361,11 +361,10 @@ ZlibBase.prototype._final = function(callback) {
 // Z_NO_FLUSH (< Z_TREES) < Z_BLOCK < Z_PARTIAL_FLUSH <
 //     Z_SYNC_FLUSH < Z_FULL_FLUSH < Z_FINISH
 const flushiness = [];
-let i = 0;
 const kFlushFlagList = [Z_NO_FLUSH, Z_BLOCK, Z_PARTIAL_FLUSH,
                         Z_SYNC_FLUSH, Z_FULL_FLUSH, Z_FINISH];
-for (const flushFlag of kFlushFlagList) {
-  flushiness[flushFlag] = i++;
+for (let i = 0; i < kFlushFlagList.length; i++) {
+  flushiness[kFlushFlagList[i]] = i;
 }
 
 function maxFlush(a, b) {