Custom social connection with reddit oauth: "too few args to sprintf"

Help
1

I’m trying to create a custom social connection.

Here are my settings:
Name: reddit
Authorization URL: https://www.reddit.com/api/v1/authorize
Token URL: https://www.reddit.com/api/v1/access_token
Scope: identity
Fetch User Profile Script:

function(accessToken, ctx, cb) {
  request.get('https://oauth.reddit.com/api/v1/me', {
    headers: {
      'Authorization': 'Bearer ' + accessToken
    }
  }, function(e, r, b) {
    if (e) return cb(e);
    if (r.statusCode !== 200) return cb(new Error('StatusCode: ' + r.statusCode));
    var profile = JSON.parse(b).data;
    profile.user_id = profile.id;
    cb(null, profile);
  });
}

and no custom headers.

After I click “authorise” on reddit’s request for permission page, I get back the following error message:

{
  "error": "server_error",
  "error_description": "too few args to sprintf"
}

Observations: The fetch user profile script doesn’t run at all, reddit redirects to /login/callback with both the code and the state included in the URL as expected.