--- old/src/hotspot/share/opto/graphKit.cpp	2018-07-04 16:48:45.857121616 +0200
+++ new/src/hotspot/share/opto/graphKit.cpp	2018-07-04 16:48:45.477121621 +0200
@@ -1772,13 +1772,21 @@
         arg = vt->allocate(this)->get_oop();
       }
     } else if (t->is_valuetypeptr()) {
-      // Constant null passed for a value type argument
-      assert(arg->bottom_type()->remove_speculative() == TypePtr::NULL_PTR, "Anything other than null?");
       ciMethod* declared_method = method()->get_method_at_bci(bci());
-      int arg_size = declared_method->signature()->arg_size_for_bc(java_bc());
-      inc_sp(arg_size); // restore arguments
-      uncommon_trap(Deoptimization::Reason_null_check, Deoptimization::Action_none);
-      return;
+      if (arg->is_ValueTypePtr()) {
+        // We are calling an Object method with a value type receiver
+        ValueTypePtrNode* vt = arg->isa_ValueTypePtr();
+        assert(i == TypeFunc::Parms && !declared_method->is_static(), "argument must be receiver");
+        assert(vt->is_allocated(&gvn()), "argument must be allocated");
+        arg = vt->get_oop();
+      } else {
+        // Constant null passed for a value type argument
+        assert(arg->bottom_type()->remove_speculative() == TypePtr::NULL_PTR, "Anything other than null?");
+        int arg_size = declared_method->signature()->arg_size_for_bc(java_bc());
+        inc_sp(arg_size); // restore arguments
+        uncommon_trap(Deoptimization::Reason_null_check, Deoptimization::Action_none);
+        return;
+      }
     }
     call->init_req(idx, arg);
     idx++;
@@ -3411,6 +3419,14 @@
 
   assert(dead_locals_are_killed(), "should kill locals before sync. point");
 
+  // We cannot lock on a value type
+  if (obj->is_ValueTypeBase()) {
+    inc_sp(1);
+    uncommon_trap(Deoptimization::Reason_class_check, Deoptimization::Action_none);
+    dec_sp(1);
+    return NULL;
+  }
+
   // Box the stack location
   Node* box = _gvn.transform(new BoxLockNode(next_monitor()));
   Node* mem = reset_memory();
@@ -3478,6 +3494,7 @@
     map()->pop_monitor();        // Kill monitor from debug info
     return;
   }
+  assert(!obj->is_ValueTypeBase(), "should not unlock on value type");
 
   // Memory barrier to avoid floating things down past the locked region
   insert_mem_bar(Op_MemBarReleaseLock);