Cannot create pull request from folk repo to origin repo with "(new branch)"

When create a pull request, from folk repo to origin repo, if the branch not exist in the origin repo, it will appear in the target branch drop down list as BranchName (new branch).

Previously you can create a pull request and will create a new branch in the origin repo when approved.

But now it doesn't work anymore. Error message shows as below and stops creating the PR.
The following error(s) occurred saving this pull request
Invalid destination branch