--- old/src/hotspot/share/runtime/thread.hpp	2020-07-21 14:10:20.842500766 +0200
+++ new/src/hotspot/share/runtime/thread.hpp	2020-07-21 14:10:20.726499034 +0200
@@ -78,6 +78,7 @@
 class vframeArray;
 class vframe;
 class javaVFrame;
+class MonitorInfo;
 
 class DeoptResourceMark;
 class jvmtiDeferredLocalVariableSet;