diff --git a/lib/6to5/file.js b/lib/6to5/file.js
index 9cdb87b108..f6b2286ee9 100644
--- a/lib/6to5/file.js
+++ b/lib/6to5/file.js
@@ -325,7 +325,7 @@ File.prototype.transform = function (ast) {
 
   this.ast = ast;
   this.lastStatements = t.getLastStatements(ast.program);
-  this.scope = new Scope(ast.program, null, this);
+  this.scope = new Scope(ast.program, ast, null, this);
   this.moduleFormatter = this.getModuleFormatter(this.opts.modules);
 
   var astRun = function (key) {
diff --git a/lib/6to5/traverse/index.js b/lib/6to5/traverse/index.js
index 57bfb767eb..06efb546e6 100644
--- a/lib/6to5/traverse/index.js
+++ b/lib/6to5/traverse/index.js
@@ -111,7 +111,7 @@ TraversalContext.prototype.visitNode = function (obj, key, opts, scope, parent,
   var ourScope = scope;
   // we're entering a new scope so let's construct it!
   if (t.isScope(node)) {
-    ourScope = new Scope(node, scope);
+    ourScope = new Scope(node, parent, scope);
   }
 
   node = this.enterNode(obj, key, node, opts.enter, parent, ourScope, state);
diff --git a/lib/6to5/traverse/scope.js b/lib/6to5/traverse/scope.js
index 6fc0ed9059..723cfb3f80 100644
--- a/lib/6to5/traverse/scope.js
+++ b/lib/6to5/traverse/scope.js
@@ -14,15 +14,18 @@ var FOR_KEYS = ["left", "init"];
  * within.
  *
  * @param {Node} block
+ * @param {Node} parentBlock
  * @param {Scope} [parent]
  * @param {File} [file]
  */
 
-function Scope(block, parent, file) {
+function Scope(block, parentBlock, parent, file) {
   this.parent = parent;
-  this.block  = block;
   this.file   = parent ? parent.file : file;
 
+  this.parentBlock = parentBlock;
+  this.block       = block;
+
   var info = this.getInfo();
   this.references = info.references;
   this.declarations = info.declarations;
@@ -197,6 +200,7 @@ Scope.prototype.getInfo = function () {
   };
 
   if (parent && t.isBlockStatement(block) && t.isFor(parent.block, { body: block })) {
+    // delegate block let declarations to the parent loop
     return info;
   }
 
@@ -240,6 +244,14 @@ Scope.prototype.getInfo = function () {
     });
   }
 
+  if (t.isFunctionExpression(block) && block.id) {
+    if (!t.isProperty(this.parentBlock, { method: true })) {
+      // SpiderMonkey AST doesn't use MethodDefinition here when it probably
+      // should since they should be semantically the same?
+      add(block.id);
+    }
+  }
+
   // Program
 
   if (t.isProgram(block)) {