Unexpected change of Last-Modified header

Hi all,

when running Jigsaw 2.0.3 as a proxy it came to my attention that the
Last-Modified header is affected when passed through Jigsaw. For
example, a HEAD request to
http://help.netscape.com/products/server/enterprise/3.5.1E-patch-readme.htm,
with no proxy, returns the following:

HTTP/1.1 200 OK
Server: Netscape-Enterprise/3.6
Date: Wed, 10 Nov 1999 11:33:13 GMT
Content-type: text/html
Last-modified: Mon, 30 Aug 1999 22:15:35 GMT
Accept-ranges: bytes

while use of Jigsaw affects the Last-Modified header as follows:

HTTP/1.1 200 OK
Date: Wed, 10 Nov 1999 11:34:00 GMT
Via: 1.1 xxxxxx:xx (Jigsaw/2.0.3)
Content-Type: text/html
Last-Modified: Wed, 10 Nov 1999 11:32:35 GMT
Accept-Ranges: bytes
Age: 24
Server: Netscape-Enterprise/3.6

Per RFC2616 (HTTP/1.1) this is buggy behaviour, since this header should
not be modified by a transparent proxy. Any thoughts?

TIA