Same header set multiple times in HST responses creates multiple values in the servlet response

I have components which set (and not add) no-cache HST response headers. That works fine when the header is set only once. However, if several components set the same header, I end up with multiple values in the servlet response:

Cache-control: no-cache, no-cache, no-cache, no-cache

I would expect that instead of appending all the values, the last one which was set would be used for the servlet response.

Also see mailing-list: http://hippo.2275632.n2.nabble.com/Multiple-values-in-servlet-response-for-same-header-set-multiple-times-in-HST-responses-td7050913.html