This is a known bug, see [this issue](https://github.com/gravitystorm/openstreetmap-carto/issues/885) which is marked as a duplicate of the more general [issue](https://github.com/gravitystorm/openstreetmap-carto/issues/688). The latter issue has been open for awhile, but is not fixed yet.yet. Nevertheless, you should add the layer tags (as hendrikklaas already wrote)

This is a known bug, see [this issue](https://github.com/gravitystorm/openstreetmap-carto/issues/885) which is marked as a duplicate of the more general [issue](https://github.com/gravitystorm/openstreetmap-carto/issues/688). The latter issue has been open for awhile, but is not fixed yet.