--- old/src/hotspot/share/gc/shared/referenceProcessor.cpp	2020-02-06 19:18:04.704550216 +0100
+++ new/src/hotspot/share/gc/shared/referenceProcessor.cpp	2020-02-06 19:18:04.536550231 +0100
@@ -1156,7 +1156,7 @@
       // Check assumption that an object is not potentially
       // discovered twice except by concurrent collectors that potentially
       // trace the same Reference object twice.
-      assert(UseConcMarkSweepGC || UseG1GC,
+      assert(UseConcMarkSweepGC || UseG1GC || UseShenandoahGC,
              "Only possible with a concurrent marking collector");
       return true;
     }