group=milestone doesn't work in default_query

[m.galante@…]

I have set this in my "trac.ini":

[query]
default_query = status!=closed&group=milestone&owner=$USER

but when I click on the "View Tickets" button, the "Group results by" box is empty. This is from my "trac.log" file:

2008-11-14 18:45:16,326 Trac[main] DEBUG: Dispatching <Request "GET u'/query'">
2008-11-14 18:45:16,326 Trac[query] DEBUG: QueryModule: Using default query: status!=closed&group=milestone&owner=$USER
2008-11-14 18:45:16,326 Trac[chrome] DEBUG: Prepare chrome data for request
2008-11-14 18:45:16,342 Trac[session] DEBUG: Retrieving session for ID u'galante'
2008-11-14 18:45:16,342 Trac[query] DEBUG: Count results in Query: 131
2008-11-14 18:45:16,342 Trac[query] DEBUG: Query SQL: SELECT t.id AS id,t.summary AS summary,t.status AS status,t.type AS type,t.priority AS priority,t.milestone AS milestone,t.component AS component,t.time AS time,t.changetime AS changetime,t.owner AS owner,priority.value AS priority_value
FROM ticket AS t
  LEFT OUTER JOIN enum AS priority ON (priority.type='priority' AND priority.name=priority)
WHERE COALESCE(t.status,'')!=u'closed' AND COALESCE(t.owner,'')=u'galante'
ORDER BY COALESCE(priority.value,'')='',CAST(priority.value AS int),t.id LIMIT 100 OFFSET 0
2008-11-14 18:45:16,358 Trac[perm] DEBUG: No policy allowed galante performing REPORT_VIEW on None
2008-11-14 18:45:16,983 Trac[perm] DEBUG: No policy allowed galante performing REPORT_CREATE on None
2008-11-14 18:45:17,187 Trac[main] DEBUG: 388 unreachable objects found.

I understand from #5998 that this should work on Trac 0.11.2, but it doesn't for me. I have tried with tracd on Windows and trac+apache on Linux, the client is Internet Explorer.