Invalid user when requesting stats server-side

[tudddorrr]

When calling SteamGameServerStats.requestUserStats(id), I get this error message: /Users/buildbot/buildslave/steam_rel_client_osx/build/src/clientdll/userstats.cpp (3639) : Assertion Failed: LoadStatsFromDisk called from invalid user: [I:0:0]

The ID is valid according to the SteamID.isValid() method and it isn't null/does exist so I'm not sure why it can't form a proper Steam ID hence [I:0:0].

Anyone had any luck with this?