diff --git a/lib/6to5/transformation/transformers/constants.js b/lib/6to5/transformation/transformers/constants.js
index 965d33dda3..15f2c8c45b 100644
--- a/lib/6to5/transformation/transformers/constants.js
+++ b/lib/6to5/transformation/transformers/constants.js
@@ -9,24 +9,27 @@ exports.ForOfStatement =
 exports.ForStatement = function (node, parent, file) {
   var constants = {};
 
-  var check = function (node, names, parent) {
-    _.each(names, function (name) {
+  var check = function (parent, names) {
+    _.each(names, function (nameNode, name) {
       if (!_.has(constants, name)) return;
       if (parent && t.isBlockStatement(parent) && parent !== constants[name]) return;
 
-      throw file.errorWithNode(node, name + " is read-only");
+      throw file.errorWithNode(nameNode, name + " is read-only");
     });
   };
 
   var getIds = function (node) {
-    return t.getIds(node, false, ["MemberExpression"]);
+    return t.getIds(node, true, ["MemberExpression"]);
   };
 
   _.each(node.body, function (child, parent) {
     if (child && t.isVariableDeclaration(child, { kind: "const" })) {
       _.each(child.declarations, function (declar) {
-        _.each(getIds(declar), function (name) {
-          check(declar, [name], parent);
+        _.each(getIds(declar), function (nameNode, name) {
+          var names = {};
+          names[name] = nameNode;
+          check(parent, names);
+
           constants[name] = parent;
         });
 
@@ -42,9 +45,10 @@ exports.ForStatement = function (node, parent, file) {
 
   traverse(node, function (child, parent) {
     if (child._ignoreConstant) return;
+    if (t.isVariableDeclaration(child)) return;
 
-    if (t.isDeclaration(child) || t.isAssignmentExpression(child)) {
-      check(child, getIds(child), parent);
+    if (t.isVariableDeclarator(child) || t.isDeclaration(child) || t.isAssignmentExpression(child)) {
+      check(parent, getIds(child));
     }
   });
 };