diff -r 0c637249d934 -r f94c7929a44b src/hotspot/share/gc/shared/gcCause.cpp
--- a/src/hotspot/share/gc/shared/gcCause.cpp	Mon Dec 10 09:37:18 2018 +0100
+++ b/src/hotspot/share/gc/shared/gcCause.cpp	Mon Dec 10 10:25:27 2018 +0100
@@ -105,6 +105,9 @@
     case _g1_humongous_allocation:
       return "G1 Humongous Allocation";
 
+    case _g1_periodic_collection:
+      return "G1 Periodic Collection";
+
     case _dcmd_gc_run:
       return "Diagnostic Command";