--- old/src/share/vm/gc_implementation/g1/heapRegion.hpp	2011-10-19 08:35:06.776259000 +0200
+++ new/src/share/vm/gc_implementation/g1/heapRegion.hpp	2011-10-19 08:35:06.338234000 +0200
@@ -431,6 +431,16 @@
     return _humongous_start_region;
   }
 
+  // Same as Space::is_in_reserved, but will use the actual size of a humongous start
+  // region rather than the end of the humongous object.
+  bool is_in_reserved_raw(const void* p) const {
+    if (startsHumongous()) {
+      return _bottom <= p && p < _orig_end;
+    } else {
+      return Space::is_in_reserved(p);
+    }
+  }
+
   // Makes the current region be a "starts humongous" region, i.e.,
   // the first region in a series of one or more contiguous regions
   // that will contain a single "humongous" object. The two parameters
--- old/src/share/vm/gc_implementation/g1/heapRegionRemSet.cpp	2011-10-19 08:35:14.700712300 +0200
+++ new/src/share/vm/gc_implementation/g1/heapRegionRemSet.cpp	2011-10-19 08:35:14.234685600 +0200
@@ -143,7 +143,7 @@
     // If the test below fails, then this table was reused concurrently
     // with this operation.  This is OK, since the old table was coarsened,
     // and adding a bit to the new table is never incorrect.
-    if (loc_hr->is_in_reserved(from)) {
+    if (loc_hr->is_in_reserved_raw(from)) {
       size_t hw_offset = pointer_delta((HeapWord*)from, loc_hr->bottom());
       CardIdx_t from_card = (CardIdx_t)
           hw_offset >> (CardTableModRefBS::card_shift - LogHeapWordSize);