diff --git a/rts/posix/Ticker.c b/rts/posix/Ticker.c
index 4adefdf9aaa014a803f8de6cc0f65fc9b14d6498..18bf1179dde55066c314029a4a4b489c89377c65 100644
--- a/rts/posix/Ticker.c
+++ b/rts/posix/Ticker.c
@@ -71,7 +71,7 @@
  * For older version of linux/netbsd without timerfd we fall back to the
  * pthread based implementation.
  */
-#if HAVE_SYS_TIMERFD_H
+#if defined(HAVE_SYS_TIMERFD_H)
 #define USE_TIMERFD_FOR_ITIMER
 #endif