diff --git a/src/pike_threadlib.h b/src/pike_threadlib.h
index f7fe02b2f11d81fd77c8c540d9da2de29e3b40cc..84d2270d125d5ffea824f6f17e65682a0167f59c 100644
--- a/src/pike_threadlib.h
+++ b/src/pike_threadlib.h
@@ -683,6 +683,7 @@ PMOD_EXPORT void pike_threads_disallow_ext (struct thread_state *ts
 #define DEFINE_MUTEX(X)
 #define DEFINE_IMUTEX(X)
 #define init_interleave_mutex(X)
+#define exit_interleave_mutex(X)
 #define LOCK_IMUTEX(X)
 #define UNLOCK_IMUTEX(X)
 #define mt_init(X)