diff -r f7e573226c2b -r 40746ab0a30b jitcraft/Heap.cpp
--- a/jitcraft/Heap.cpp	Sat Jul 14 18:43:34 2012 -0700
+++ b/jitcraft/Heap.cpp	Sat Jul 14 21:01:52 2012 -0700
@@ -312,19 +312,16 @@
         while (bits) {
             uint32 bit = FindRightmostBit(bits);
             Address object = HeapChunk::FromMarkBit(chunk, markbits, bit);
+
+            assert(object >= freeStart);
             if (freeStart != object)
                 space->markRegionFree(freeStart, object - freeStart);
+
             Object *obj = reinterpret_cast<Object *>(object);
             freeStart = object + SizeOfObject(obj, obj->map());
 
+            // Since black is 10, we never need to clear the next bit.
             bits &= ~(1 << bit);
-            if (bits == HeapChunk::kMarkBitsPerWord - 1) {
-                // This bit is the last bit on this word, so bump up to the
-                // next word and exclude the first bit.
-                markbits++;
-                assert(markbits < markbitsEnd);
-                bits = *markbits & ~(1 << 0);
-            }
         }
         markbits++;
         bits = *markbits;