#ifdef USE_ITHREADS
# define OP_REFCNT_INIT MUTEX_INIT(&PL_op_mutex)
-# define OP_REFCNT_LOCK MUTEX_LOCK(&PL_op_mutex)
-# define OP_REFCNT_UNLOCK MUTEX_UNLOCK(&PL_op_mutex)
+# ifdef PERL_CORE
+# define OP_REFCNT_LOCK MUTEX_LOCK(&PL_op_mutex)
+# define OP_REFCNT_UNLOCK MUTEX_UNLOCK(&PL_op_mutex)
+# else
+# define OP_REFCNT_LOCK op_refcnt_lock()
+# define OP_REFCNT_UNLOCK op_refcnt_unlock()
+# endif
# define OP_REFCNT_TERM MUTEX_DESTROY(&PL_op_mutex)
#else
# define OP_REFCNT_INIT NOOP