--- old/src/share/vm/gc_implementation/g1/g1GCPhaseTimes.cpp	2015-03-03 17:05:48.559761743 +0100
+++ new/src/share/vm/gc_implementation/g1/g1GCPhaseTimes.cpp	2015-03-03 17:05:48.455761748 +0100
@@ -125,6 +125,10 @@
 
 template <class T>
 void WorkerDataArray<T>::verify() {
+  if (!_enabled) {
+    return;
+  }
+
   for (uint i = 0; i < _length; i++) {
     assert(_data[i] != WorkerDataArray<T>::uninitialized(),
         err_msg("Invalid data for worker %u in '%s'", i, _title));
@@ -312,11 +316,15 @@
 
 G1GCPhaseTimesTracker::G1GCPhaseTimesTracker(G1GCPhaseTimes* phase_times, G1GCPhaseTimes::GCPhases phase, uint worker_id) :
     _phase_times(phase_times), _phase(phase), _worker_id(worker_id) {
-  _start_time = os::elapsedTime();
+  if (_phase_times != NULL) {
+    _start_time = os::elapsedTime();
+  }
 }
 
 G1GCPhaseTimesTracker::~G1GCPhaseTimesTracker() {
-  _phase_times->record_time_secs(_phase, _worker_id, os::elapsedTime() - _start_time);
+  if (_phase_times != NULL) {
+    _phase_times->record_time_secs(_phase, _worker_id, os::elapsedTime() - _start_time);
+  }
 }
 
 void G1GCPhasePrinter::print_single_length(G1GCPhaseTimes::GCPhases phase_id, WorkerDataArray<double>* phase) {