Hi,

GNU Emacs 27.0.50 (build 1, x86_64-w64-mingw32) of 2017-11-08
git master, check out 6/7 Nov
(937cdfc4005f324170966cbc0fdffc20cf9ee786)

How to repeat the bug:
Emacs -Q
C-x b, then, C-g


The verson by 14 Oct git has no such issue.

Best Regards
Shuguang