Static content not gzipped to IE9 from IIS7

Question

I've enabled gzip compression in IIS using the config settings specified in this answer.

When I request a text file using Firefox, I can see in Firebug that the response is gzipped:

But when I request the same text file using IE9, the dev tools show it is not gzipped:

Why is IIS not sending the txt file compressed? Am I missing some IIS setting? Is my browser misconfigured?

Answer 1

I'd compare both requests using Fiddler since IE dev tools doesn't seem to be showing all response headers