diff --git a/src/source.c b/src/source.c
index f028c6b8c..debd2b1ec 100644
--- a/src/source.c
+++ b/src/source.c
@@ -2341,7 +2341,7 @@ _dispatch_kevent_timer_set_delay(_dispatch_kevent_qos_s *ke, uint64_t delay,
 {
 	// call to update nows[]
 	_dispatch_source_timer_now(nows, DISPATCH_TIMER_KIND_WALL);
-#if KEVENT_NSEC_NOT_SUPPORTED
+#ifdef KEVENT_NSEC_NOT_SUPPORTED
 	// adjust nsec based delay to msec based and ignore leeway
 	delay /= 1000000L;
 	if ((int64_t)(delay) <= 0) {