Exclude constraint names for suggestion results

I'm working on context-aware suggestions in MarkLogic. In the suggestion request I'm sending the query containing filters selected by user. One of the filters - date filter - uses constraint with computed buckets. My request looks like this:

POST http://<marklogic>:<port>/LATEST/suggest?limit=200&partial-q=ord
Content-Type: application/json
Accept: application/json

{
  "search": {
    "query": {
      "queries": [
        {
          "and-query": [
            {
              "value-query": {
                "json-property": "order_status",
                "text": [
                  "completed"
                ]
              }
            },
            {
              "value-query": {
                "json-property": "product_type",
                "text": [
                  "Foo"
                ]
              }
            },
            {
              "range-constraint-query": {
                "constraint-name": "order_date",
                "value": "7Days"
              }
            }
          ]
        }
      ]
    },
    "options": {
      "default-suggestion-source": {
        "range": {
          "type": "xs:string",
          "field": {
            "name": "suggestion"
          }
        }
      },
      "constraint": [
        {
          "name": "order_date",
          "range": {
            "type": "xs:dateTime",
            "facet": false,
            "json-property": "order_date",
            "computed-bucket": [
              {
                "name": "7Days",
                "ge": "-P7D",
                "anchor": "start-of-day"
              },
              {
                "name": "30Days",
                "ge": "-P30D",
                "anchor": "start-of-day"
              },
              {
                "name": "180Days",
                "ge": "-P180D",
                "anchor": "start-of-day"
              }
            ]
          }
        }
      ]
    }
  }
}

In the response, among expected values ("suggestion" filed contains paths to all field I want to get suggestions from), I also get "order_date:". Even if I add:

      "suggestion-source": [
        {
          "ref": "order_date"
        }
     ]

I still get it in the results. The only difference is that I get no values if partial-q=order_date:

Any tips how can I get rid of this "order_date:" among results?