--- old/src/share/vm/gc_implementation/g1/concurrentMark.cpp	2015-04-14 09:59:16.819766480 +0200
+++ new/src/share/vm/gc_implementation/g1/concurrentMark.cpp	2015-04-14 09:59:16.740765093 +0200
@@ -114,7 +114,7 @@
 }
 
 size_t CMBitMap::compute_size(size_t heap_size) {
-  return heap_size / mark_distance();
+  return ReservedSpace::allocation_align_size_up(heap_size / mark_distance());
 }
 
 size_t CMBitMap::mark_distance() {