--- a/src/hotspot/share/gc/shared/collectedHeap.cpp	Mon May 07 14:57:23 2018 +0200
+++ b/src/hotspot/share/gc/shared/collectedHeap.cpp	Mon May 07 14:57:25 2018 +0200
@@ -652,3 +652,7 @@
 void CollectedHeap::unpin_object(JavaThread* thread, oop obj) {
   ShouldNotReachHere();
 }
+
+void CollectedHeap::deduplicate_string(oop str) {
+  // Do nothing, unless overridden in subclass.
+}