diff --git a/include/unistd.h b/include/unistd.h
index 4b2b89f6ec..4d0f739a70 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -66,6 +66,7 @@
 #define _POSIX_THREAD_CPUTIME _POSIX_VERSION
 #define _POSIX_REALTIME_SIGNALS _POSIX_VERSION
 #define _POSIX_THREAD_PRIORITY_SCHEDULING _POSIX_VERSION
+#define _POSIX_SEMAPHORES _POSIX_VERSION
 
 #ifdef CONFIG_FS_AIO
 #  define _POSIX_ASYNCHRONOUS_IO _POSIX_VERSION