--- a/src/hotspot/share/oops/instanceKlass.cpp	Mon Nov 25 12:32:40 2019 +0100
+++ b/src/hotspot/share/oops/instanceKlass.cpp	Mon Nov 25 12:33:15 2019 +0100
@@ -2200,7 +2200,7 @@
       if (impl != NULL && !impl->is_loader_alive()) {
         // NULL this field, might be an unloaded klass or NULL
         Klass* volatile* klass = adr_implementor();
-        if (Atomic::cmpxchg((Klass*)NULL, klass, impl) == impl) {
+        if (Atomic::cmpxchg(klass, impl, (Klass*)NULL) == impl) {
           // Successfully unlinking implementor.
           if (log_is_enabled(Trace, class, unload)) {
             ResourceMark rm;