diff --git a/src/heap_bitmap.h b/src/heap_bitmap.h
index 29a7b1f..4333199 100644
--- a/src/heap_bitmap.h
+++ b/src/heap_bitmap.h
@@ -69,11 +69,16 @@
     // Find and replace a bitmap pointer, this is used by for the bitmap swapping in the GC.
     void ReplaceBitmap(SpaceBitmap* old_bitmap, SpaceBitmap* new_bitmap);
 
-   private:
-    void AddSpaceBitmap(SpaceBitmap* space) {
-      bitmaps_.push_back(space);
+    HeapBitmap(Heap* heap) : heap_(heap) {
+
     }
 
+   private:
+
+    const Heap* const heap_;
+
+    void AddSpaceBitmap(SpaceBitmap* bitmap);
+
     typedef std::vector<SpaceBitmap*> Bitmaps;
     Bitmaps bitmaps_;