Twitter not sending email address of user in some cases



If a user has already authorized my twitter app for permissions lets say read and write and If I add a new permission for asking email from user, then after re authentication of my twitter app twitter is not returning email address in user data. While if the user has not authorized my twitter app before and If he authorize my twitter app now then I am getting email address in user data.

If i revoke the permission my twitter app in case of already authorized twitter app and then I authorize twitter app again with read, write and email permissions then twitter is sending email address of user.