diff --git a/include/v8.h b/include/v8.h
index ec2f48d796..430f410a6e 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -863,13 +863,13 @@ class Value : public Data {
    * Returns true if this value is the undefined value.  See ECMA-262
    * 4.3.10.
    */
-  V8EXPORT bool IsUndefined() const;
+  inline bool IsUndefined() const;
 
   /**
    * Returns true if this value is the null value.  See ECMA-262
    * 4.3.11.
    */
-  V8EXPORT bool IsNull() const;
+  inline bool IsNull() const;
 
    /**
    * Returns true if this value is true.
@@ -983,7 +983,11 @@ class Value : public Data {
   V8EXPORT bool StrictEquals(Handle<Value> that) const;
 
  private:
+  inline bool QuickIsUndefined() const;
+  inline bool QuickIsNull() const;
   inline bool QuickIsString() const;
+  V8EXPORT bool FullIsUndefined() const;
+  V8EXPORT bool FullIsNull() const;
   V8EXPORT bool FullIsString() const;
 };
 
@@ -3894,6 +3898,7 @@ class Internals {
   static const int kStringResourceOffset =
       InternalConstants<kApiPointerSize>::kStringResourceOffset;
 
+  static const int kOddballKindOffset = 3 * kApiPointerSize;
   static const int kForeignAddressOffset = kApiPointerSize;
   static const int kJSObjectHeaderSize = 3 * kApiPointerSize;
   static const int kFullStringRepresentationMask = 0x07;
@@ -3901,8 +3906,12 @@ class Internals {
 
   static const int kJSObjectType = 0xaa;
   static const int kFirstNonstringType = 0x80;
+  static const int kOddballType = 0x82;
   static const int kForeignType = 0x85;
 
+  static const int kUndefinedOddballKind = 5;
+  static const int kNullOddballKind = 3;
+
   static inline bool HasHeapObjectTag(internal::Object* value) {
     return ((reinterpret_cast<intptr_t>(value) & kHeapObjectTagMask) ==
             kHeapObjectTag);
@@ -3922,6 +3931,11 @@ class Internals {
     return ReadField<uint8_t>(map, kMapInstanceTypeOffset);
   }
 
+  static inline int GetOddballKind(internal::Object* obj) {
+    typedef internal::Object O;
+    return SmiValue(ReadField<O*>(obj, kOddballKindOffset));
+  }
+
   static inline void* GetExternalPointerFromSmi(internal::Object* value) {
     const uintptr_t address = reinterpret_cast<uintptr_t>(value);
     return reinterpret_cast<void*>(address >> kPointerToSmiShift);
@@ -4203,6 +4217,42 @@ String::ExternalStringResource* String::GetExternalStringResource() const {
 }
 
 
+bool Value::IsUndefined() const {
+#ifdef V8_ENABLE_CHECKS
+  return FullIsUndefined();
+#else
+  return QuickIsUndefined();
+#endif
+}
+
+bool Value::QuickIsUndefined() const {
+  typedef internal::Object O;
+  typedef internal::Internals I;
+  O* obj = *reinterpret_cast<O**>(const_cast<Value*>(this));
+  if (!I::HasHeapObjectTag(obj)) return false;
+  if (I::GetInstanceType(obj) != I::kOddballType) return false;
+  return (I::GetOddballKind(obj) == I::kUndefinedOddballKind);
+}
+
+
+bool Value::IsNull() const {
+#ifdef V8_ENABLE_CHECKS
+  return FullIsNull();
+#else
+  return QuickIsNull();
+#endif
+}
+
+bool Value::QuickIsNull() const {
+  typedef internal::Object O;
+  typedef internal::Internals I;
+  O* obj = *reinterpret_cast<O**>(const_cast<Value*>(this));
+  if (!I::HasHeapObjectTag(obj)) return false;
+  if (I::GetInstanceType(obj) != I::kOddballType) return false;
+  return (I::GetOddballKind(obj) == I::kNullOddballKind);
+}
+
+
 bool Value::IsString() const {
 #ifdef V8_ENABLE_CHECKS
   return FullIsString();
diff --git a/src/api.cc b/src/api.cc
index c7252ba3ff..3826a1c97b 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -2101,17 +2101,21 @@ bool StackFrame::IsConstructor() const {
 
 // --- D a t a ---
 
-bool Value::IsUndefined() const {
+bool Value::FullIsUndefined() const {
   if (IsDeadCheck(i::Isolate::Current(), "v8::Value::IsUndefined()")) {
     return false;
   }
-  return Utils::OpenHandle(this)->IsUndefined();
+  bool result = Utils::OpenHandle(this)->IsUndefined();
+  ASSERT_EQ(result, QuickIsUndefined());
+  return result;
 }
 
 
-bool Value::IsNull() const {
+bool Value::FullIsNull() const {
   if (IsDeadCheck(i::Isolate::Current(), "v8::Value::IsNull()")) return false;
-  return Utils::OpenHandle(this)->IsNull();
+  bool result = Utils::OpenHandle(this)->IsNull();
+  ASSERT_EQ(result, QuickIsNull());
+  return result;
 }
 
 
diff --git a/src/objects.h b/src/objects.h
index d682cde0f8..80d1fd47d0 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -680,6 +680,7 @@ const int kExternalArrayTypeCount =
 
 STATIC_CHECK(JS_OBJECT_TYPE == Internals::kJSObjectType);
 STATIC_CHECK(FIRST_NONSTRING_TYPE == Internals::kFirstNonstringType);
+STATIC_CHECK(ODDBALL_TYPE == Internals::kOddballType);
 STATIC_CHECK(FOREIGN_TYPE == Internals::kForeignType);
 
 
@@ -7636,6 +7637,10 @@ class Oddball: public HeapObject {
                               kToNumberOffset + kPointerSize,
                               kSize> BodyDescriptor;
 
+  STATIC_CHECK(kKindOffset == Internals::kOddballKindOffset);
+  STATIC_CHECK(kNull == Internals::kNullOddballKind);
+  STATIC_CHECK(kUndefined == Internals::kUndefinedOddballKind);
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(Oddball);
 };