Bool field as Creteria for Collection

I have added my fields/indexes to plone.app.querystring, and all works, except from 'Bool fields/indexes'.

  • My field 'closed' has two values, which shows up in the catalog as 'True' and 'False'
  • 'closed' shows up in Collection Search Term (as Yes and No), but nothing is 'found'.

Is there anthing more I have to do?

 <records interface="plone.app.querystring.interfaces.IQueryField"
          prefix="plone.app.querystring.field.closed">
   <value key="title">Closed</value>
   <value key="description">Closed (no)</value>
   <value key="enabled">True</value>
   <value key="operations">
       <element>plone.app.querystring.operation.boolean.isTrue</element>
       <element>plone.app.querystring.operation.boolean.isFalse</element> 
   </value>
   <value key="group">Metadata</value>
 </records>

Update: To test, I added the same code for 'excluded from nav', with same result: It does not work. Plone 6.0.05

 <records interface="plone.app.querystring.interfaces.IQueryField" prefix="plone.app.querystring.field.exclude_from_nav">
    <value key="title" i18n:translate="">Hidden from navigation</value>
    <value key="description" i18n:translate="">Find items that are hidden from the navigation tree.</value>
    <value key="enabled">True</value>
    <value key="sortable">False</value>
    <value key="operations">
      <element>plone.app.querystring.operation.boolean.isTrue</element>
      <element>plone.app.querystring.operation.boolean.isFalse</element>
    </value>
    <value key="group" i18n:translate="">Metadata</value>
  </records>

UPDATE: This site has been updated from 6.0.?, Adding a new site (even on the same Zope seems to work, which is a bit strange.