Searchkick Advanced mapping being applied to all models

I have multiple models for multiple indices using searchkick. In one of the models I'm trying to use a custom analyzer, so I'm defining the advanced mapping as shown in the docs

searchkick merge_mappings: true, mappings: {
    properties: {
      name: {type: "keyword"}
    }
  }

My this works fine, but when I look at my index in kibana, the mapping has shown up on all of my indices, not just the model that I specified it on. Does anyone know how to keep the mapping on just one model?