diff --git a/src/heap.cc b/src/heap.cc
index b1096b37e2..f48d9cc452 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -3414,7 +3414,7 @@ void Heap::FlushNumberStringCache() {
   // Flush the number to string cache.
   int len = number_string_cache()->length();
   for (int i = 0; i < len; i++) {
-    number_string_cache()->set_undefined(this, i);
+    number_string_cache()->set_undefined(i);
   }
 }
 
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index f065da1f94..4eb51b549e 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -2590,7 +2590,7 @@ void MarkCompactCollector::ClearNonLivePrototypeTransitions(Map* map) {
   for (int i = new_number_of_transitions * step;
        i < number_of_transitions * step;
        i++) {
-    prototype_transitions->set_undefined(heap_, header + i);
+    prototype_transitions->set_undefined(header + i);
   }
 }
 
diff --git a/src/objects-inl.h b/src/objects-inl.h
index b165ad4638..f629d9f19f 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -2092,28 +2092,21 @@ void FixedArray::NoWriteBarrierSet(FixedArray* array,
 
 
 void FixedArray::set_undefined(int index) {
-  ASSERT(map() != HEAP->fixed_cow_array_map());
-  set_undefined(GetHeap(), index);
-}
-
-
-void FixedArray::set_undefined(Heap* heap, int index) {
+  ASSERT(map() != GetHeap()->fixed_cow_array_map());
   ASSERT(index >= 0 && index < this->length());
-  ASSERT(!heap->InNewSpace(heap->undefined_value()));
-  WRITE_FIELD(this, kHeaderSize + index * kPointerSize,
-              heap->undefined_value());
+  ASSERT(!GetHeap()->InNewSpace(GetHeap()->undefined_value()));
+  WRITE_FIELD(this,
+              kHeaderSize + index * kPointerSize,
+              GetHeap()->undefined_value());
 }
 
 
 void FixedArray::set_null(int index) {
-  set_null(GetHeap(), index);
-}
-
-
-void FixedArray::set_null(Heap* heap, int index) {
   ASSERT(index >= 0 && index < this->length());
-  ASSERT(!heap->InNewSpace(heap->null_value()));
-  WRITE_FIELD(this, kHeaderSize + index * kPointerSize, heap->null_value());
+  ASSERT(!GetHeap()->InNewSpace(GetHeap()->null_value()));
+  WRITE_FIELD(this,
+              kHeaderSize + index * kPointerSize,
+              GetHeap()->null_value());
 }
 
 
diff --git a/src/objects.h b/src/objects.h
index 988f1ab636..00c534d139 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2913,11 +2913,7 @@ class FixedArray: public FixedArrayBase {
 
   // Setters for frequently used oddballs located in old space.
   inline void set_undefined(int index);
-  // TODO(isolates): duplicate.
-  inline void set_undefined(Heap* heap, int index);
   inline void set_null(int index);
-  // TODO(isolates): duplicate.
-  inline void set_null(Heap* heap, int index);
   inline void set_the_hole(int index);
 
   inline Object** GetFirstElementAddress();