MockServer cannot detect the expanded property when filtering

I defined a list like the following:

<List id="list"
  width="auto"
  items="{
    path: '/CategorySet',
    parameters: {
      expand: 'CategoryType,Status,Articles'
    },
    filters: [
      {
        path: 'CategoryType/Name',
        operator: 'EQ',
        value1: 'Frei'
      }
    ],
    sorter: {
      path: 'Name',
      descending: false
    },
    groupHeaderFactory: '.createGroupHeader'
  }">

Despite I have expanded CategoryType but the filter will cause the following error:

MockServer: navigation property 'CategoryType' was not expanded, so Property 'Name' not found -

I used Web IDE and the project is a simple Master-Details project from the template ones!

Any suggestion?