diff --git a/ext/posix/sched.c b/ext/posix/sched.c
index 13b196b..6901589 100644
--- a/ext/posix/sched.c
+++ b/ext/posix/sched.c
@@ -21,9 +21,7 @@
 
 #include <config.h>
 
-#include <unistd.h>	/* for _POSIX_PRIORITY_SCHEDULING */
-
-#ifdef _POSIX_PRIORITY_SCHEDULING
+#if HAVE_SCHED_GETSCHEDULER || HAVE_SCHED_SETSCHEDULER
 #include <sched.h>
 #endif