Bug in git-diff output

I tried to get a diff between HEAD and the current version of my
project, so I did "git diff".

It's a web project with a CSS file that contains the following CSS rule:

a[href^=tel] {
    color:inherit;
    text-decoration:none;
}

Now, whenever I do "git diff", it will always show the a[href^=tel]
part and mess up the output, even when I didn't change anything near
that line. The problem is easily reproducable in a newly created
repository.

git --version
git version 1.9.1