diff --git a/sys/sys/unistd.h b/sys/sys/unistd.h
index 70e3ef7e2839..378308de8204 100644
--- a/sys/sys/unistd.h
+++ b/sys/sys/unistd.h
@@ -68,7 +68,7 @@
 #define	_POSIX_PRIORITY_SCHEDULING	200112L
 #define	_POSIX_RAW_SOCKETS		200112L
 #define	_POSIX_REALTIME_SIGNALS		200112L
-#define	_POSIX_SEMAPHORES		-1
+#define	_POSIX_SEMAPHORES		200112L
 #define	_POSIX_SHARED_MEMORY_OBJECTS	200112L
 #define	_POSIX_SPORADIC_SERVER		-1
 #define	_POSIX_SYNCHRONIZED_IO		-1