diff --git a/deps/v8/src/objects.cc b/deps/v8/src/objects.cc
index d3e6492479..6314955b13 100644
--- a/deps/v8/src/objects.cc
+++ b/deps/v8/src/objects.cc
@@ -1720,11 +1720,13 @@ MaybeObject* JSObject::AddProperty(String* name,
                                    Object* value,
                                    PropertyAttributes attributes,
                                    StrictModeFlag strict_mode,
-                                   JSReceiver::StoreFromKeyed store_mode) {
+                                   JSReceiver::StoreFromKeyed store_mode,
+                                   ExtensibilityCheck extensibility_check) {
   ASSERT(!IsJSGlobalProxy());
   Map* map_of_this = map();
   Heap* heap = GetHeap();
-  if (!map_of_this->is_extensible()) {
+  if (extensibility_check == PERFORM_EXTENSIBILITY_CHECK &&
+      !map_of_this->is_extensible()) {
     if (strict_mode == kNonStrictMode) {
       return value;
     } else {
@@ -1763,7 +1765,8 @@ MaybeObject* JSObject::SetPropertyPostInterceptor(
     String* name,
     Object* value,
     PropertyAttributes attributes,
-    StrictModeFlag strict_mode) {
+    StrictModeFlag strict_mode,
+    ExtensibilityCheck extensibility_check) {
   // Check local property, ignore interceptor.
   LookupResult result(GetIsolate());
   LocalLookupRealNamedProperty(name, &result);
@@ -1778,7 +1781,8 @@ MaybeObject* JSObject::SetPropertyPostInterceptor(
       SetPropertyViaPrototypes(name, value, attributes, strict_mode, &done);
   if (done) return result_object;
   // Add a new real property.
-  return AddProperty(name, value, attributes, strict_mode);
+  return AddProperty(name, value, attributes, strict_mode,
+                     MAY_BE_STORE_FROM_KEYED, extensibility_check);
 }
 
 
@@ -1935,7 +1939,8 @@ MaybeObject* JSObject::SetPropertyWithInterceptor(
       this_handle->SetPropertyPostInterceptor(*name_handle,
                                               *value_handle,
                                               attributes,
-                                              strict_mode);
+                                              strict_mode,
+                                              PERFORM_EXTENSIBILITY_CHECK);
   RETURN_IF_SCHEDULED_EXCEPTION(isolate);
   return raw_result;
 }
@@ -3664,11 +3669,14 @@ MaybeObject* JSObject::GetHiddenPropertiesDictionary(bool create_if_absent) {
   MaybeObject* dict_alloc = StringDictionary::Allocate(kInitialSize);
   StringDictionary* dictionary;
   if (!dict_alloc->To<StringDictionary>(&dictionary)) return dict_alloc;
-  // Using AddProperty or SetPropertyPostInterceptor here could fail, because
-  // object might be non-extensible.
-  return HasFastProperties()
-      ? AddFastProperty(GetHeap()->hidden_symbol(), dictionary, DONT_ENUM)
-      : AddSlowProperty(GetHeap()->hidden_symbol(), dictionary, DONT_ENUM);
+  MaybeObject* store_result =
+      SetPropertyPostInterceptor(GetHeap()->hidden_symbol(),
+                                 dictionary,
+                                 DONT_ENUM,
+                                 kNonStrictMode,
+                                 OMIT_EXTENSIBILITY_CHECK);
+  if (store_result->IsFailure()) return store_result;
+  return dictionary;
 }
 
 
@@ -3697,7 +3705,8 @@ MaybeObject* JSObject::SetHiddenPropertiesDictionary(
       SetPropertyPostInterceptor(GetHeap()->hidden_symbol(),
                                  dictionary,
                                  DONT_ENUM,
-                                 kNonStrictMode);
+                                 kNonStrictMode,
+                                 OMIT_EXTENSIBILITY_CHECK);
   if (store_result->IsFailure()) return store_result;
   return this;
 }
diff --git a/deps/v8/src/objects.h b/deps/v8/src/objects.h
index 9aac37fcce..15ecdd1412 100644
--- a/deps/v8/src/objects.h
+++ b/deps/v8/src/objects.h
@@ -1369,6 +1369,13 @@ class JSReceiver: public HeapObject {
     CERTAINLY_NOT_STORE_FROM_KEYED
   };
 
+  // Internal properties (e.g. the hidden properties dictionary) might
+  // be added even though the receiver is non-extensible.
+  enum ExtensibilityCheck {
+    PERFORM_EXTENSIBILITY_CHECK,
+    OMIT_EXTENSIBILITY_CHECK
+  };
+
   // Casting.
   static inline JSReceiver* cast(Object* obj);
 
@@ -1567,7 +1574,8 @@ class JSObject: public JSReceiver {
       String* name,
       Object* value,
       PropertyAttributes attributes,
-      StrictModeFlag strict_mode);
+      StrictModeFlag strict_mode,
+      ExtensibilityCheck extensibility_check);
 
   static Handle<Object> SetLocalPropertyIgnoreAttributes(
       Handle<JSObject> object,
@@ -1959,7 +1967,8 @@ class JSObject: public JSReceiver {
       Object* value,
       PropertyAttributes attributes,
       StrictModeFlag strict_mode,
-      StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED);
+      StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED,
+      ExtensibilityCheck extensibility_check = PERFORM_EXTENSIBILITY_CHECK);
 
   // Convert the object to use the canonical dictionary
   // representation. If the object is expected to have additional properties
diff --git a/deps/v8/test/mjsunit/regress/regress-2156.js b/deps/v8/test/mjsunit/regress/regress-2156.js
new file mode 100644
index 0000000000..3482571130
--- /dev/null
+++ b/deps/v8/test/mjsunit/regress/regress-2156.js
@@ -0,0 +1,39 @@
+// Copyright 2012 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax --harmony-collections
+
+var key1 = {};
+var key2 = {};
+var map = new WeakMap;
+
+// Adding hidden properties preserves map sharing. Putting the key into
+// a WeakMap will cause the first hidden property to be added.
+assertTrue(%HaveSameMap(key1, key2));
+map.set(key1, 1);
+map.set(key2, 2);
+assertTrue(%HaveSameMap(key1, key2));