--- original_query.inc	2009-03-25 00:06:24.000000000 +0100
+++ query.inc	2009-04-29 13:46:51.000000000 +0200
@@ -936,6 +936,10 @@ class views_query {
         $string = "COUNT($string)";
         $has_aggregate = TRUE;
       }
+      else if (!empty($field['sum'])) {
+        $string = "SUM($string)";
+        $has_aggregate = TRUE;
+      }
       else if (!empty($field['aggregate'])) {
         $has_aggregate = TRUE;
       }