zlib.output-compression ON = Non-working sitemap.xml

Setting zlib compression on inside of php itself causes requests for sitemap.xml to come back as jibberish.

It looks to be a case of double-gzipping, since the files output into /tmp are .xml.gz already (I assume the xmlsitemap module is zipping them down when it writes them), and then when php fulfills the request and outputs back to the client, they're getting squished down again.