diff --git a/lib/zlib.js b/lib/zlib.js
index 559f6c2d5f3056..a918411160c76d 100644
--- a/lib/zlib.js
+++ b/lib/zlib.js
@@ -779,6 +779,6 @@ const bkeys = Object.keys(constants);
 for (var bk = 0; bk < bkeys.length; bk++) {
   var bkey = bkeys[bk];
   Object.defineProperty(module.exports, bkey, {
-    enumerable: true, value: constants[bkey], writable: false
+    enumerable: false, value: constants[bkey], writable: false
   });
 }