diff --git a/app/config/schema/schema.json b/app/config/schema/schema.json
index 8f7f6b3b2..dfe32ca39 100644
--- a/app/config/schema/schema.json
+++ b/app/config/schema/schema.json
@@ -71,7 +71,7 @@
         "matchgrid_id": { "notnull": false },
         "username": {
           "XXX": "we don't currently define username anywhere, ie there is no users table",
-          "type": "string", "size": 128
+          "type": "string", "size": 320
         },
         "permission": { "type": "string", "size": 2 }
       },
@@ -248,4 +248,4 @@
 "XXX": "a list of tables to manually drop, not yet implemented"
     }
   ]
-}
\ No newline at end of file
+}