We were getting the following harmless error in our logs:

[...] sygnal.gcmpushkin 109 - WARNING - The following configuration fields are not understood: {'max_connections'}

However this option is documented in the sample config:

and used in the codebase:

So it seems like we just forgot to add it to this list while adding the option 🙂

(If you're wondering why inflight_request_limit isn't in this dict either, that's because it's shared across both APNs and GCM pushkin types :)