X-Accel-Redirect not passing Content-Type?

[Kon Wilms]

I'm having an odd problem with x-accel-redirect when using PHP to
process the request:

Setting the headers in the php script:
header("Content-Type: blah/blah");

Result page header still comes through as:
Content-Type: text/html

Hence I am seeing .html tacked on to attachment filename downloads in
Chrome and Safari.

Is x-accel ignoring the Content-Type?

Cheers
Kon