Index: CoWork.h
===================================================================
--- CoWork.h	(revision 11440)
+++ CoWork.h	(working copy)
@@ -155,7 +155,10 @@
 	~AsyncWork()                                    { if(imp) imp->co.Cancel(); }
 };
 
-#if !defined(__clang__) || 1000 * __clang_major__ + __clang_minor__ > 3004
+#if !defined(__clang__) || 1000 * __clang_major__ + __clang_minor__ >= 3004
+#if defined(__clang__) && defined(_LIBCPP_STD_VER) && _LIBCPP_STD_VER <= 11
+#error The C++14 capable compiler and library required. Try to compile with using -std=c++14 or -std=c++1y (for Clang 3.4 and earlier).
+#endif
 
 template< class Function, class... Args>
 AsyncWork<std::result_of_t<std::decay_t<Function>(std::decay_t<Args>...)>>