Missing 'grant_type' parameter value - still?

[ethrbunny]

(Ive seen a few entries related to this error but the fixes don't see to be working. )

In a nutshell- trying to use the refresh token to get the access token. Using 

https://api.fitbit.com/oauth2/token

for the URL.

Hitting this error: 

Missing 'grant_type' parameter value. Visit https://dev.fitbit.com/docs/oauth2 for more information on the Fitbit Web API authorization process.

I tried the POST request using both json and text for the body. I've checked the values sent by POSTing to posttestserver.dev. Everything is there.

[ethrbunny]

(for posterity)

Change the 'content-type' to 'application/x-www-form-urlencoded' and make sure the body params are a & delimited string.

Sending json doesn't work.