--- a/boost/accumulators/statistics/mean.hpp	2008-06-19 20:47:42.000000000 -0700
+++ b/boost/accumulators/statistics/mean.hpp	2009-07-13 19:01:55.000000000 -0700
@@ -142,8 +142,8 @@
 //
 namespace extract
 {
-    extractor<tag::mean> const mean = {};
-    extractor<tag::mean_of_weights> const mean_of_weights = {};
+    extern extractor<tag::mean> const mean = {};
+    extern extractor<tag::mean_of_weights> const mean_of_weights = {};
     BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, mean_of_variates, (typename)(typename))
 }