--- a/src/hotspot/share/gc/g1/heapRegion.cpp	Fri Dec 14 16:52:17 2018 -0800
+++ b/src/hotspot/share/gc/g1/heapRegion.cpp	Mon Dec 17 11:37:40 2018 +0100
@@ -877,8 +877,10 @@
 }
 
 G1ContiguousSpace::G1ContiguousSpace(G1BlockOffsetTable* bot) :
+  _top(NULL),
   _bot_part(bot, this),
-  _par_alloc_lock(Mutex::leaf, "OffsetTableContigSpace par alloc lock", true)
+  _par_alloc_lock(Mutex::leaf, "OffsetTableContigSpace par alloc lock", true),
+  _pre_dummy_top(NULL)
 {
 }