CARD POST chinese utf-8 trello REST API?

Is there away to support sending chinese character via the API? i’ve tried setting the header to support charset=utf-8 but this doesn’t do anything the chinese text is just converted into question marks?

fetch('https://api.trello.com/1/cards?idList=5abbe4b7ddc1b351ef961414&key=APIKey&token=APIToken', { method: 'POST', headers: { 'Accept': 'application/json' } })

ended up just encoding my text with HTTP.