Users are not mapped in imported git repo

I've imported a repo from github with a bunch of existing commits, but all committers, including myself, appear as unknown in the commit stream, i.e. not mapped to a bitbucket profile.

1. The emails on existing commits are correct: I have added and verified emails that I've used to commit via github to my account, bitbucket still can't map the commits by that email to the actual profile.
2. If, after importing the repo, I make a new commit with the same email, the committer is mapped correctly to my profile.

I know I can work around it by adding aliases of all committers manually per repo, but I feel like I should not have to, all the information is already there, and Bitbucket should be able to figure it out.