diff --git a/solr.cfg b/solr.cfg
index 7a1bf60..93d4a6b 100644
--- a/solr.cfg
+++ b/solr.cfg
@@ -76,3 +76,4 @@ index =
     name:mail_date        type:date stored:true
     name:meeting_date     type:date stored:true
     name:sortable_title   type:string stored:true
+    name:internal_reference_number type:string stored:true