Lock themes do not work for custom connections

[david-bc]

Lock has a "Last time you logged in with" feature. Themes on the login button work for Social Connections provided by Auth0 but do not work for configured themes from the Custom Social Connections plugin. If I add a custom Slack connection and theme it in Lock this is the result:

Setup

1. https://api.slack.com/apps
2. Add features and functionality > Permissions
3. Scopes > Add the identity.basic permission

Connection Configuration

Name: Slack
Client ID: https://api.slack.com/apps/ > App Credentials
** Client Secret**: https://api.slack.com/apps/ > App Credentials
Authorization URL: https://slack.com/oauth/authorize
Token URL: https://slack.com/api/oauth.access
Scope: identity.basic
Fetch User Profile Script:

function(accessToken, ctx, cb) {
  var profile = {
    user_id: ctx.user.id,
    team_id: ctx.team.id,
    name: ctx.user.name,
    ctx: ctx
  }
  cb(null, profile);
}

Lock Theme Configuration

Use the following values as the Lock theme option:

{
  theme: {
    authButtons: {
      Slack: {
        primaryColor: "#443142",
        foregroundColor: "#FFFFFF",
        icon: "http://icon-icons.com/icons2/923/PNG/128/slack_icon-icons.com_72028.png"
      }
    }
  }
}