diff --git a/headers/posix/unistd.h b/headers/posix/unistd.h
index 4de488a158..9c8fc77099 100644
--- a/headers/posix/unistd.h
+++ b/headers/posix/unistd.h
@@ -43,9 +43,9 @@
 #define _POSIX_THREADS						(200112L)
 #define _POSIX_MAPPED_FILES					(200809L)
 #define _POSIX_THREAD_PROCESS_SHARED		(200809L)
-#undef  _POSIX_THREAD_ATTR_STACKADDR		/* currently unsupported */
+#define _POSIX_THREAD_ATTR_STACKADDR		(-1)	/* currently unsupported */
 #define _POSIX_THREAD_ATTR_STACKSIZE		(200809L)
-#undef  _POSIX_THREAD_PRIORITY_SCHEDULING	/* currently unsupported */
+#define _POSIX_THREAD_PRIORITY_SCHEDULING	(-1)	/* currently unsupported */
 #define _POSIX_REALTIME_SIGNALS				(200809L)
 #define _POSIX_MEMORY_PROTECTION			(200809L)
 #define _POSIX_MONOTONIC_CLOCK				(200809L)
diff --git a/src/system/libroot/posix/unistd/conf.cpp b/src/system/libroot/posix/unistd/conf.cpp
index a5728928cb..5ae51e9f68 100644
--- a/src/system/libroot/posix/unistd/conf.cpp
+++ b/src/system/libroot/posix/unistd/conf.cpp
@@ -156,13 +156,11 @@ __sysconf(int name)
 		case _SC_THREAD_STACK_MIN:
 			return MIN_USER_STACK_SIZE;
 		case _SC_THREAD_ATTR_STACKADDR:
-			return -1;
-				// currently unsupported
+			return _POSIX_THREAD_ATTR_STACKADDR;
 		case _SC_THREAD_ATTR_STACKSIZE:
 			return _POSIX_THREAD_ATTR_STACKSIZE;
 		case _SC_THREAD_PRIORITY_SCHEDULING:
-			return -1;
-				// currently unsupported
+			return _POSIX_THREAD_PRIORITY_SCHEDULING;
 		case _SC_REALTIME_SIGNALS:
 			return _POSIX_REALTIME_SIGNALS;
 		case _SC_MEMORY_PROTECTION: