Bug report: clicking merge twice on a pull request leads to two mergers

Hi GitHub Support!

I merged this pull request. Right after clicking merge I noticed I had written a typo. Since the textbox was still editable, I corrected it and hit the merge button again. Looking at the commit history, Github successfully merged the pull request with the typo but sill flagged the pull request as being unmerged. Not knowing what to do I closed the request.

Tip for reproducing the bug: be lighting fast. I used my browser’s autocorrect.

Thank you for your help!

PS.
I followed this page’s instructions to submit this bug report. Do let me know if I’m in the wrong place or missed something.