diff --git a/src/mrw/checkcxx11.hxx b/src/mrw/checkcxx11.hxx
index f4ea966..99b030f 100644
--- a/src/mrw/checkcxx11.hxx
+++ b/src/mrw/checkcxx11.hxx
@@ -27,7 +27,8 @@
 #  endif
 
 #  if __cplusplus==1
-#    warning your compiler has a know bug, please upgrade
+#    warning your compiler has a know bug, please upgrade to gcc >= 4.7
+#    warning see __cplusplus in http://gcc.gnu.org/gcc-4.7/changes.html
 #  endif