diff --git a/libc3/facts.c b/libc3/facts.c
index fee9bff..fb9aa80 100644
--- a/libc3/facts.c
+++ b/libc3/facts.c
@@ -374,7 +374,7 @@ void facts_lock_unlock_w (s_facts *facts)
assert(facts);
facts->rwlock_count--;
if (! facts->rwlock_count) {
- facts->rwlock_thread = NULL;
+ facts->rwlock_thread = 0;
if (pthread_rwlock_unlock(&facts->rwlock))
err(1, "facts_lock_unlock_w: pthread_rwlock_unlock");
}