[TYPO3-Solr] numericRange only on integer?

[Tim Werdin]

I have the following TS:

price {
  label = Preis
  field = price_floatS
  type = numericRange
  numericRange {
    min = 99
    max = 699
    gap = 100
  }
}

But when I try to open the search page on FE I got a lot of error 
messages that the response is not a valid JSON.
Isn't it possible to make a range on a float? Even if I user integer 
min, max and gap?

Regards
Tim