Index: concept_check.hpp
===================================================================
--- concept_check.hpp	(revision 60959)
+++ concept_check.hpp	(working copy)
@@ -330,7 +330,12 @@
       {
           f(arg);
       }
-      
+
+#if BOOST_WORKAROUND(__GNUC__, BOOST_TESTED_AT(4))
+      // Construktor to make gcc happy (warning: non-static reference ‘const double& boost::UnaryFunction<YourClassHere>::arg’ in class without a constructor [-Wuninitialized]
+      UnaryFunction() {};
+#endif
+
       Func f;
       Arg arg;
   };