diff --git a/packages/babylon/src/parser/node.js b/packages/babylon/src/parser/node.js
index c5bfb2a82b..3ddd6038c2 100644
--- a/packages/babylon/src/parser/node.js
+++ b/packages/babylon/src/parser/node.js
@@ -32,13 +32,13 @@ class Node implements NodeBase {
   __clone(): this {
     // $FlowIgnore
     const node2: any = new Node();
-    for (const key in this) {
+    Object.keys(this).forEach(key => {
       // Do not clone comments that are already attached to the node
       if (commentKeys.indexOf(key) < 0) {
         // $FlowIgnore
         node2[key] = this[key];
       }
-    }
+    });
 
     return node2;
   }
diff --git a/packages/babylon/src/tokenizer/state.js b/packages/babylon/src/tokenizer/state.js
index e2ad59f9f8..0041dcfbf8 100644
--- a/packages/babylon/src/tokenizer/state.js
+++ b/packages/babylon/src/tokenizer/state.js
@@ -185,7 +185,7 @@ export default class State {
 
   clone(skipArrays?: boolean): State {
     const state = new State();
-    for (const key in this) {
+    Object.keys(this).forEach(key => {
       // $FlowIgnore
       let val = this[key];
 
@@ -195,7 +195,7 @@ export default class State {
 
       // $FlowIgnore
       state[key] = val;
-    }
+    });
     return state;
   }
 }