--- old/src/share/vm/gc/g1/g1RemSet.inline.hpp	2015-11-03 17:15:25.400158972 +0100
+++ new/src/share/vm/gc/g1/g1RemSet.inline.hpp	2015-11-03 17:15:25.320158575 +0100
@@ -60,6 +60,8 @@
   assert(_g1->is_in_reserved(obj), "must be in heap");
 #endif // ASSERT
 
+  assert(from->is_in_reserved(p) || from->is_starts_humongous(), "p is not in from");
+
   HeapRegion* to = _g1->heap_region_containing(obj);
   if (from != to) {
     assert(to->rem_set() != NULL, "Need per-region 'into' remsets.");