diff --git a/lib/6to5/traverse/index.js b/lib/6to5/traverse/index.js
index 38bcf14997..204969d2a2 100644
--- a/lib/6to5/traverse/index.js
+++ b/lib/6to5/traverse/index.js
@@ -39,25 +39,23 @@ function traverse(parent, opts, scope) {
       // replace node
       var maybeReplace = function (result) {
         if (result === false) return;
+        if (result == null) return;
 
-        if (result != null) {
-          updated = true;
+        var isArray = _.isArray(result);
 
-          var isArray = _.isArray(result);
+        // inherit comments from original node to the first replacement node
+        var inheritTo = result;
+        if (isArray) inheritTo = result[0];
+        if (inheritTo) t.inheritsComments(inheritTo, node);
 
-          // inherit comments from original node to the first replacement node
-          var inheritTo = result;
-          if (isArray) inheritTo = result[0];
-          if (inheritTo) t.inheritsComments(inheritTo, node);
+        // replace the node
+        node = obj[key] = result;
+        updated = true;
 
-          // replace the node
-          node = obj[key] = result;
-
-          // we're replacing a statement or block node with an array of statements so we better
-          // ensure that it's a block
-          if (isArray && _.contains(t.STATEMENT_OR_BLOCK_KEYS, key) && !t.isBlockStatement(obj)) {
-            t.ensureBlock(obj, key);
-          }
+        // we're replacing a statement or block node with an array of statements so we better
+        // ensure that it's a block
+        if (isArray && _.contains(t.STATEMENT_OR_BLOCK_KEYS, key) && !t.isBlockStatement(obj)) {
+          t.ensureBlock(obj, key);
         }
       };
 
@@ -70,7 +68,8 @@ function traverse(parent, opts, scope) {
         },
 
         remove: function () {
-          stopped = removed = true;
+          this.stop();
+          removed = true;
         }
       };
 
@@ -84,12 +83,12 @@ function traverse(parent, opts, scope) {
         maybeReplace(result);
 
         if (removed) {
-          delete obj[key];
+          obj[key] = null;
           updated = true;
         }
 
         // stop iteration
-        if (stopped || result === false) return;
+        if (stopped) return;
       }
 
       // traverse node
@@ -106,7 +105,9 @@ function traverse(parent, opts, scope) {
         handle(nodes, i);
       }
 
-      if (updated) parent[key] = _.flatten(parent[key]);
+      if (updated) {
+        parent[key] = _.flatten(parent[key]);
+      }
     } else {
       handle(parent, key);
     }
@@ -155,7 +156,7 @@ traverse.hasType = function (tree, type, blacklistTypes) {
     enter: function (node) {
       if (node.type === type) {
         has = true;
-        return false;
+        this.stop();
       }
     }
   });