When using response.appendHeader, Zope appends the new value following an ",\r\n\t" which splits the header over multiple lines. While this behaviour is standards compliant, it causes problems for both Varnish [1] and Nginx [2] which may then mangle the header value. In fact the HTTP 1.0 spec notes that splitting over multiple lines in not recommended [3], though the HTTP 1.1 spec does not mention this explicitly, though it does say [4]: "Applications ought to follow "common form", where one is known or indicated, when generating HTTP constructs, since there might exist some implementations that fail to accept anything" Are there any objections to me applying the attached patch to Zope 2.13 and trunk? Laurence [1] http://www.varnish-cache.org/trac/ticket/905 [2] http://nginx.org/pipermail/nginx-devel/2011-April/000859.html [3] http://tools.ietf.org/html/rfc1945#section-4.2 [4] http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html