Index: /trunk/src/VBox/Main/src-server/MachineImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/src-server/MachineImpl.cpp	(revision 54174)
+++ /trunk/src/VBox/Main/src-server/MachineImpl.cpp	(revision 54175)
@@ -11191,7 +11191,4 @@
                )
             {
-                ComObjPtr<Medium> parent = pMedium->i_getParent();
-                AutoWriteLock parentLock(parent COMMA_LOCKVAL_SRC_POS);
-
                 /* update the appropriate lock list */
                 MediumLockList *pMediumLockList;
@@ -11207,5 +11204,5 @@
                         fMediaNeedsLocking = true;
                     }
-                    rc = pMediumLockList->Update(parent, false);
+                    rc = pMediumLockList->Update(pMedium->getParent(), false);
                     AssertComRC(rc);
                     rc = pMediumLockList->Append(pMedium, true);