Custom Header Lines (http response)

Apologies if this was already answered - I searched, but was unable to find a similar scenario to mine.

A partner is making a call to a service in our wM4.6 environment.

webMethods is returing:

body

[INDENT]bytes
[/INDENT]header

[INDENT]lines

[INDENT]Content-type
Connection
Content-Length
[/INDENT]status

[/INDENT]Now, the partner wants us to add a custom header line:

body

[INDENT]bytes
[/INDENT]header

[INDENT]lines

[INDENT]Content-type
Connection
Content-Length
User-defined value
[/INDENT]status

[/INDENT]How can I add this additional header-line? I tried pub.flow:setResponse, which does not help. I also used a custom java code to hdr.setResponse, but this just changes the “statusMessage”.

Please help.

Piara