Override gravatar url to use SSL if gitlab has the SSL flag set to true.

app/helpers/application_helper.rb

@@ -37,7 +37,7 @@ module ApplicationHelper
     if !Gitlab.config.gravatar.enabled || user_email.blank?
       'no_avatar.png'
     else
-      gravatar_url = request.ssl? ? Gitlab.config.gravatar.ssl_url : Gitlab.config.gravatar.plain_url
+      gravatar_url = request.ssl? || Gitlab.config.gitlab.https ? Gitlab.config.gravatar.ssl_url : Gitlab.config.gravatar.plain_url
       user_email.strip!
       sprintf gravatar_url, hash: Digest::MD5.hexdigest(user_email.downcase), size: size
     end