diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h
--- a/sys/sys/cdefs.h
+++ b/sys/sys/cdefs.h
@@ -213,12 +213,7 @@
 #endif
 
 #if !__has_extension(c_thread_local)
-/*
- * XXX: Some compilers (Clang 3.3, GCC 4.7) falsely announce C++11 mode
- * without actually supporting the thread_local keyword. Don't check for
- * the presence of C++11 when defining _Thread_local.
- */
-#if /* (defined(__cplusplus) && __cplusplus >= 201103L) || */ \
+#if (defined(__cplusplus) && __cplusplus >= 201103L) ||
     __has_extension(cxx_thread_local)
 #define	_Thread_local		thread_local
 #else