Manual HTTP proxy configuration broken?

I have been unable to change the configuration from SOCKS proxy to HTTP proxy. Torbrowser would simply claim there isn't any HTTP proxy answering while telnet confirms there is. Is this a known bug? Is this related to ticket legacy/trac#8511 (moved) or legacy/trac#8228 (moved)? Is this a new one? Is it happening in my implementation only? This bug tracker is so huge, it's hard to figure out.

I'm running the current version, based on FX 31.6.0.450.

Trac:
Username: vynX