diff --git a/headers/posix/unistd.h b/headers/posix/unistd.h
index 63889cec25..fd2c0684cb 100644
--- a/headers/posix/unistd.h
+++ b/headers/posix/unistd.h
@@ -44,7 +44,7 @@
 #define _POSIX_THREADS						(200112L)
 #define _POSIX_MAPPED_FILES					(200809L)
 #define _POSIX_THREAD_PROCESS_SHARED		(200809L)
-#define _POSIX_THREAD_ATTR_STACKADDR		(-1)	/* currently unsupported */
+#define _POSIX_THREAD_ATTR_STACKADDR		(200809L)
 #define _POSIX_THREAD_ATTR_STACKSIZE		(200809L)
 #define _POSIX_THREAD_PRIORITY_SCHEDULING	(-1)	/* currently unsupported */
 #define _POSIX_REALTIME_SIGNALS				(200809L)