+#if I_THREADSAFE
+/* We must use preexistent global mutexes or we will never be able to destroy
+ * them. */
+# if I_HAS_PERL(5, 9, 3)
+# define I_LOADED_LOCK MUTEX_LOCK(&PL_my_ctx_mutex)
+# define I_LOADED_UNLOCK MUTEX_UNLOCK(&PL_my_ctx_mutex)
+# else
+# define I_LOADED_LOCK OP_REFCNT_LOCK
+# define I_LOADED_UNLOCK OP_REFCNT_UNLOCK
+# endif
+#else
+# define I_LOADED_LOCK NOOP
+# define I_LOADED_UNLOCK NOOP
+#endif
+