diff --git a/lock.h b/lock.h
index e6f58f2..d39f07b 100644
--- a/lock.h
+++ b/lock.h
@@ -23,7 +23,7 @@ typedef pthread_mutex_t mutex_t;
 // If this pthread implementation has a static initializer for recursive
 // mutexes, use that, otherwise fall back to the portable version
 #	ifdef PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP
-#		define INIT_LOCK(x) x = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP
+#		define INIT_LOCK(x) x = (pthread_mutex_t)PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP
 #	elif defined(PTHREAD_RECURSIVE_MUTEX_INITIALIZER)
 #		define INIT_LOCK(x) x = (pthread_mutex_t)PTHREAD_RECURSIVE_MUTEX_INITIALIZER
 #	else