Setting SELinux context of loop-mounted ISO filesystem

[Deron Meranda]

I'm trying to mount some ISO files using the loop device.  However
I can't seem to get the context= option on the mount to work.  As
such the mounted files have no SELinux context set.  In particular
I'm trying the following,

  mount -t iso9660 \
     -o context=system_u:object_r:httpd_sys_content_t,loop,ro,noexec,nodev,nosuid
 \
     /path/to/file.iso  /mountpoint

I'm running in enforcing mode with selinux-policy-targeted-1.17.30-2.93

How can one mount an ISO image file and force all files to appear
to have a particular SELinux context?

-- 
Deron Meranda