How do you set world seed with GemCore on a dedicated server?

[HawkwardAlaskan]

I've tried adding

worldseed = "12345"

to worldgenoverride.lua in both shards but I get

WARNING! Found value '12345' for setting 'worldseed', but this is not a valid value. Use one of {}.

More than that, the Caves shard takes it and appears to be using the seed (if console output is to be trusted), but the Master shard is always a random seed. They've been setup with the same overrides and values; copy pasted. Even tried only specifying the worldseed and nothing else. Tried disabling all other mods, but then even Caves stopped working.