--- a/src/hotspot/share/gc/z/zHeapIterator.cpp	Sun Oct 27 12:13:51 2019 +0000
+++ b/src/hotspot/share/gc/z/zHeapIterator.cpp	Mon Oct 28 11:21:23 2019 +0100
@@ -126,7 +126,7 @@
 
 ZHeapIterator::ZHeapIterator() :
     _visit_stack(),
-    _visit_map() {}
+    _visit_map(ZAddressOffsetMax) {}
 
 ZHeapIterator::~ZHeapIterator() {
   ZVisitMapIterator iter(&_visit_map);