Using inherited API key causes a question mark to be added to the request URL

When I make a call to an API using an inherited API key, the call fails with an HTTP 400 error. The error from the server states “route /foo/bar? not supported”. Note the trailing “?” on the URL.

If I disabled the inherited API key, and just add it as a regular HTTP header, the call works fine.

I can see in tcpdump that yaak is adding the “?” to the URL:

GET /v1/publicip/ip? HTTP/1.1
user-agent: yaak
accept: */*
x-api-key: obscuredkeygoeshere
accept-encoding: gzip, br, deflate
host: example.lan:8001

This only seems to be problem for one particular app for me (Gluetun), and others just seem to ignore it. But if there are no querystring parameters, Yaak should probably not be adding a “?”