Change in "git checkout" behaviour between 1.6.0.2 and 1.6.0.3

The following works fine with 1.6.0.2 and before, but not 1.6.0.3 or
later:

	git clone -n git git-test
        cd git-test
        git checkout -b work v1.6.0.2

When it breaks, the error is:

	error: Entry '.gitignore' would be overwritten by merge. Cannot merge.

I'm guessing it's a bug rather than a deliberate change?