Deleting remote master branch, refused due to being the current branch

How do I delete a remote master branch from GitHub/Bitbucket?

I'm trying:

# git push bb --delete master
remote: bb/acl: user is allowed. accepted payload.[K
remote: error: refusing to delete the current branch: refs/heads/master[K
To ssh://[email protected]/user/reponame.git
 ! [remote rejected] master (deletion of the current branch prohibited)
error: failed to push some refs to 'ssh://[email protected]/user/reponame.git' 

Also I tried

git push bb :master

But all this does not work.

Note: for Bitbucket, you would change the default branch by accessing the settings of your repository, and changing the branch at the "Main branch" combo box.

Once the main branch is no longer master, then you can push and remove master.

MarsAndBack confirms in the comments this applies to GitHub as well.

In the settings block on the options tap in the settings page (well, just click on the Settings tab on your GitHub repository page), you are able to change the default branch (you need to have the other default branch on GitHub as well).

After you have done that, you are able to remove it:

$ git push bb :master