diff --git a/src/gmp.c b/src/gmp.c
index c9659aef6..b45465aa5 100644
--- a/src/gmp.c
+++ b/src/gmp.c
@@ -10192,6 +10192,10 @@ buffer_aggregate_wc_xml (GString *xml, iterator_t* aggregate,
 
   g_string_append_printf (xml, "<aggregate>");
 
+  g_string_append_printf (xml,
+                          "<data_type>%s</data_type>",
+                          type);
+
   g_string_append_printf (xml,
                           "<group_column>%s</group_column>",
                           group_column);
@@ -10509,6 +10513,10 @@ buffer_aggregate_xml (GString *xml, iterator_t* aggregate, const gchar* type,
 
   g_string_append_printf (xml, "<aggregate>");
 
+  g_string_append_printf (xml,
+                          "<data_type>%s</data_type>",
+                          type);
+
   for (index = 0; index < data_columns->len ;index ++)
     {
       gchar *column_name = g_array_index (data_columns, gchar*, index);