TypeError: can't compare offset-naive and offset-aware datetimes

[sentry]

Sentry Issue: BOT-1NW

TypeError: can't compare offset-naive and offset-aware datetimes
  File "discord/client.py", line 351, in _run_event
    await coro(*args, **kwargs)
  File "bot/exts/moderation/modlog.py", line 408, in on_member_join
    difference = abs(relativedelta(now, member.created_at))
  File "dateutil/relativedelta.py", line 154, in __init__
    if dt1 < dt2:

Unhandled exception in on_member_join.