bottle: 'after_request' runs but headers don't get set

import bottle


app = bottle.Bottle()

@app.hook('after_request')
def fn():
    print(dict(bottle.response.headers))
    bottle.response.headers['abc'] = 'yes'
    print(dict(bottle.response.headers))


@app.get('/')
def asdf():
    return ''


app.run()

This code runs properly. I’m able to get the headers when I make a request from another program. However if I change the route to

@app.get('/')
def asdf():
    bottle.abort(424)

The hook gets run since I can see it in the server process log

Bottle v0.12.13 server starting up (using WSGIRefServer())...
Listening on http://127.0.0.1:8080/
Hit Ctrl-C to quit.

{}
{'abc': 'yes'}
127.0.0.1 - - [15/Jan/2019 21:23:03] "GET / HTTP/1.1" 424 726

but the header is not received in the program which made the call. That program is also quiet simple. curl http://localhost:8080 -D-

I saw #978 and was facing the same problem. Some of the UI frameworks using our APIs break if the error response does not have CORS headers.

Am I doing something wrong?