bash completion on 4.0 broken?

When I try

    git show --pretty=<TAB><TAB>

I get a list of filenames and not the list of pretty formats.

I've debugged a little and see that the cur variable in _git_show () is set to '=' when it should be '--pretty='. So it looks like something is causing the command line to be split weirdly. Looking at the bash NEWS[1] for 4.0 I see

i.  The programmable completion code now uses the same set of characters as
    readline when breaking the command line into a list of words.

which causes me to believe this is why it's broken now. I've tried removing '=' from COMP_WORDBREAKS and that shows the list of formats correctly, but then causes the entire '--pretty=' to be replaced with the selected format.

Anyone else seeing the same problem or is my system just b0rked?

$ bash --version GNU bash, version 4.0.35(2)-release (x86_64-pc-linux-gnu)

References: [1] http://tiswww.case.edu/php/chet/bash/NEWS