Http integration custom header 2

I need to send two values in the HTTP Header to my server. How can I specify in TTN HTTP Integration to send two fields as customer header information . It should look like this

Header Values
field1 . aa
field2 bb

How do I have to define it in TTN Integration in the Field Custom Header Name and Custom Header Value?

passing one field is working, however I need two fields and I tried it with comma separated which doesn’t work like
Customer Header field
field1, field2
Customer Header value
aa, bb

Any recommendation highly welcome