diff --git a/lib/util.js b/lib/util.js
index 9e61bd83e05541..b243c81dd50e7b 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -677,12 +677,13 @@ function formatArray(ctx, value, recurseTimes, visibleKeys, keys) {
   if (remaining > 0) {
     output.push(`... ${remaining} more item${remaining > 1 ? 's' : ''}`);
   }
-  keys.forEach(function(key) {
+  for (var n = 0; n < keys.length; n++) {
+    var key = keys[n];
     if (typeof key === 'symbol' || !key.match(/^\d+$/)) {
       output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
                                  key, true));
     }
-  });
+  }
   return output;
 }
 
@@ -713,10 +714,10 @@ function formatSet(ctx, value, recurseTimes, visibleKeys, keys) {
     var str = formatValue(ctx, v, nextRecurseTimes);
     output.push(str);
   });
-  keys.forEach(function(key) {
+  for (var n = 0; n < keys.length; n++) {
     output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
-                               key, false));
-  });
+                               keys[n], false));
+  }
   return output;
 }
 
@@ -730,10 +731,10 @@ function formatMap(ctx, value, recurseTimes, visibleKeys, keys) {
     str += formatValue(ctx, v, nextRecurseTimes);
     output.push(str);
   });
-  keys.forEach(function(key) {
+  for (var n = 0; n < keys.length; n++) {
     output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
-                               key, false));
-  });
+                               keys[n], false));
+  }
   return output;
 }
 
@@ -763,10 +764,10 @@ function formatPromise(ctx, value, recurseTimes, visibleKeys, keys) {
       output.push(str);
     }
   }
-  keys.forEach(function(key) {
+  for (var n = 0; n < keys.length; n++) {
     output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
-                               key, false));
-  });
+                               keys[n], false));
+  }
   return output;
 }