--- old/src/hotspot/share/gc/g1/g1GCPhaseTimes.cpp	2018-04-11 13:43:33.073486625 +0200
+++ new/src/hotspot/share/gc/g1/g1GCPhaseTimes.cpp	2018-04-11 13:43:32.808478488 +0200
@@ -166,9 +166,12 @@
 }
 
 #define ASSERT_PHASE_UNINITIALIZED(phase) \
-    assert(_gc_par_phases[phase]->get(i) == uninitialized, "Phase " #phase " reported for thread that was not started");
+    assert(_gc_par_phases[phase] == NULL || _gc_par_phases[phase]->get(i) == uninitialized, "Phase " #phase " reported for thread that was not started");
 
 double G1GCPhaseTimes::worker_time(GCParPhases phase, uint worker) {
+  if (_gc_par_phases[phase] == NULL) {
+    return 0.0;
+  }
   double value = _gc_par_phases[phase]->get(worker);
   if (value != WorkerDataArray<double>::uninitialized()) {
     return value;
@@ -191,6 +194,7 @@
       double worker_known_time =
           worker_time(ExtRootScan, i)
           + worker_time(SATBFiltering, i)
+          + worker_time(ScanHCC, i)
           + worker_time(UpdateRS, i)
           + worker_time(ScanRS, i)
           + worker_time(CodeRoots, i)
@@ -203,6 +207,7 @@
       ASSERT_PHASE_UNINITIALIZED(GCWorkerEnd);
       ASSERT_PHASE_UNINITIALIZED(ExtRootScan);
       ASSERT_PHASE_UNINITIALIZED(SATBFiltering);
+      ASSERT_PHASE_UNINITIALIZED(ScanHCC);
       ASSERT_PHASE_UNINITIALIZED(UpdateRS);
       ASSERT_PHASE_UNINITIALIZED(ScanRS);
       ASSERT_PHASE_UNINITIALIZED(CodeRoots);