--- a/boost/accumulators/statistics/sum.hpp	2008-06-19 20:47:42.000000000 -0700
+++ b/boost/accumulators/statistics/sum.hpp	2009-07-13 18:58:03.000000000 -0700
@@ -104,9 +104,9 @@
 //
 namespace extract
 {
-    extractor<tag::sum> const sum = {};
-    extractor<tag::sum_of_weights> const sum_of_weights = {};
-    extractor<tag::abstract_sum_of_variates> const sum_of_variates = {};
+    extern extractor<tag::sum> const sum = {};
+    extern extractor<tag::sum_of_weights> const sum_of_weights = {};
+    extern extractor<tag::abstract_sum_of_variates> const sum_of_variates = {};
 }
 
 using extract::sum;