--- a/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp	Thu Jun 07 11:20:30 2018 +0200
+++ b/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp	Thu Jun 07 11:20:55 2018 +0200
@@ -1651,7 +1651,11 @@
   }
 
   if (has_overflown()) {
-    // We can not trust g1_is_alive if the marking stack overflowed
+    // We can not trust g1_is_alive and the contents of the heap if the marking stack
+    // overflowed while processing references. Exit the VM.
+    fatal("Overflow during reference processing, can not continue. Please "
+          "increase MarkStackSizeMax (current value: " SIZE_FORMAT ") and "
+          "restart.", MarkStackSizeMax);
     return;
   }