Build Tag API response doesn't match docs

I’m executing a query against /repo/my%2Frepo/builds?limit=1 and I am getting back a response that contains a list of builds, with the tag field looking like this:

"tag": {
        "@type": "tag",
        "@representation": "minimal",
        "repository_id": 7605320,
        "name": "v5.0.11",
        "last_build_id": null

The docs ( suggest that the tag field is a string, and the API bindings I am using (shuheiktgw/go-travis) are expecting a string and failing to unmarshal the response. Did this change recently?