--- old/src/share/vm/gc_implementation/g1/g1RemSet.cpp	2014-08-14 13:40:45.103197843 +0200
+++ new/src/share/vm/gc_implementation/g1/g1RemSet.cpp	2014-08-14 13:40:45.022195463 +0200
@@ -540,6 +540,12 @@
 
 bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i,
                            bool check_for_refs_into_cset) {
+  assert(_g1->is_in_exact(_ct_bs->addr_for(card_ptr)),
+         err_msg("Card at "PTR_FORMAT" index "SIZE_FORMAT" representing heap at "PTR_FORMAT" (%u) must be in committed heap",
+                 p2i(card_ptr),
+                 _ct_bs->index_for(_ct_bs->addr_for(card_ptr)),
+                 _ct_bs->addr_for(card_ptr),
+                 _g1->addr_to_region(_ct_bs->addr_for(card_ptr))));
 
   // If the card is no longer dirty, nothing to do.
   if (*card_ptr != CardTableModRefBS::dirty_card_val()) {