spell check of commit messages does not work

corresponding option in options is activated

typing any nonsense word as commit message does not rise red wavy highlight

it is freshly installed Win 10 machine, the spell checker worked before I reinstalled the system (there was Win 7 updated to 10 earlier)

checked with any recent Source tree version 3.x also with 3.4.3 (which is not yet available on the drop down list below)