--- old/src/hotspot/share/services/memoryManager.cpp	2018-10-19 10:54:06.000000000 -0400
+++ new/src/hotspot/share/services/memoryManager.cpp	2018-10-19 10:54:05.000000000 -0400
@@ -210,7 +210,9 @@
 
 void GCMemoryManager::gc_begin(bool recordGCBeginTime, bool recordPreGCUsage,
                                bool recordAccumulatedGCTime) {
-  assert(_last_gc_stat != NULL && _current_gc_stat != NULL, "Just checking");
+  // Inactive memory managers (concurrent in G1 legacy mode) will not be initialized.
+  if (_last_gc_stat == NULL && _current_gc_stat == NULL) return;
+
   if (recordAccumulatedGCTime) {
     _accumulated_timer.start();
   }
@@ -243,6 +245,8 @@
                              bool recordGCEndTime, bool countCollection,
                              GCCause::Cause cause,
                              bool allMemoryPoolsAffected) {
+  if (_last_gc_stat == NULL && _current_gc_stat == NULL) return;
+
   if (recordAccumulatedGCTime) {
     _accumulated_timer.stop();
   }