diff --git a/lib/6to5/transformers/block-binding.js b/lib/6to5/transformers/block-binding.js
index cf44b6e019..f829d62a33 100644
--- a/lib/6to5/transformers/block-binding.js
+++ b/lib/6to5/transformers/block-binding.js
@@ -24,7 +24,7 @@ var hasLet = function (nodes) {
 };
 
 exports.Program = function (node) {
-  if (hasLet(node.body)) node.body = buildNode(node.body).node;
+   if (hasLet(node.body)) node.body = buildNode(node.body).node;
 };
 
 exports.BlockStatement = function (node, parent, opts, generateUid) {
@@ -38,7 +38,7 @@ exports.BlockStatement = function (node, parent, opts, generateUid) {
   var built = buildNode(node.body, true);
   node.body = built.node;
 
-  traverse.replace(built.body, function (node) {
+  traverse(built.body, function (node) {
     if (node.type === "ContinueStatement") {
       return b.returnStatement(null);
     }
@@ -51,7 +51,7 @@ exports.BlockStatement = function (node, parent, opts, generateUid) {
       b.variableDeclarator(id, b.literal(false))
     ]));
 
-    traverse.replace(built.body, function (node) {
+    traverse(built.body, function (node) {
       if (node.type === "BreakStatement") {
         return b.returnStatement(b.assignmentExpression("=", id, b.literal(true)));
       }
diff --git a/lib/6to5/traverse/index.js b/lib/6to5/traverse/index.js
index 89778910b8..0fd057cad8 100644
--- a/lib/6to5/traverse/index.js
+++ b/lib/6to5/traverse/index.js
@@ -1,12 +1,12 @@
 var VISITOR_KEYS = require("./visitor-keys");
 var _            = require("lodash");
 
-var traverse = module.exports = function (parent, callback, blacklistTypes) {
+var traverse = module.exports = function (parent, callbacks, blacklistTypes) {
   if (!parent) return;
 
   if (_.isArray(parent)) {
     _.each(parent, function (node) {
-      traverse(node, callback, blacklistTypes);
+      traverse(node, callbacks, blacklistTypes);
     });
     return;
   }
@@ -14,6 +14,10 @@ var traverse = module.exports = function (parent, callback, blacklistTypes) {
   var keys = VISITOR_KEYS[parent.type] || [];
   blacklistTypes = blacklistTypes || [];
 
+  if (_.isFunction(callbacks)) {
+    callbacks = { enter: callbacks };
+  }
+
   _.each(keys, function (key) {
     var nodes = parent[key];
     if (!nodes) return;
@@ -21,14 +25,23 @@ var traverse = module.exports = function (parent, callback, blacklistTypes) {
     var handle = function (obj, key) {
       var node = obj[key];
       if (!node) return;
+
+      // type is blacklisted
       if (blacklistTypes.indexOf(node.type) >= 0) return;
 
-      // strict references in case the callback modified/replaced the node
+      // enter
+      var result = callbacks.enter(node, parent, obj, key);
 
-      var result = callback(obj[key], parent, obj, key);
+      // stop iteration
       if (result === false) return;
 
-      traverse(obj[key], callback, blacklistTypes);
+      // replace node
+      if (result != null) node = obj[key] = result;
+
+      traverse(node, callbacks, blacklistTypes);
+
+      // exit
+      if (callbacks.exit) callbacks.exit(node, parent, obj, key);
     };
 
     if (_.isArray(nodes)) {
@@ -36,6 +49,7 @@ var traverse = module.exports = function (parent, callback, blacklistTypes) {
         handle(nodes, i);
       });
 
+      // remove deleted nodes
       parent[key] = _.flatten(parent[key]).filter(function (node) {
         return node !== traverse.Delete;
       });
@@ -73,11 +87,3 @@ traverse.hasType = function (tree, type, blacklistTypes) {
 
   return has;
 };
-
-traverse.replace = function (node, callback, blacklistTypes) {
-  traverse(node, function (node, parent, obj, key) {
-    var result = callback(node, parent);
-    if (result === false) return false;
-    if (result != null) obj[key] = result;
-  }, blacklistTypes);
-};
diff --git a/lib/6to5/util.js b/lib/6to5/util.js
index 8d5c1f33f7..5a2bab5d55 100644
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -112,7 +112,7 @@ exports.template = function (name, nodes, keepExpression) {
   template = _.cloneDeep(template);
 
   if (!_.isEmpty(nodes)) {
-    traverse.replace(template, function (node) {
+    traverse(template, function (node) {
       if (node.type === "Identifier" && _.has(nodes, node.name)) {
         var newNode = nodes[node.name];
         if (_.isString(newNode)) {