Cannot use function_score on scaled_float field

[surabaya]

I have a field with the following mapping:

"price": {
    "properties": {
        "price_amount": {
            "type": "scaled_float",
            "scaling_factor": 100 
        }   
    }   
}

And I'm trying to use the gauss scoring function as follows:

"query": {
  "function_score": {
    "functions": [
      {   
        "gauss": {
          "price.price_amount": { 
            "origin": "50", 
            "offset": "50",
            "scale":  "20"
          }   
        }   
      }   
    ]   
  }   
}

But I'm getting this error from ES:

field [price.price_amount] is of type [indexed,omitNorms], but only numeric types are supported.

I'm confused about this because from what I understand, scaled_float is a numeric type.