Door's too small??

Built my first SV with an interior. Placed a manual door on the side of the hull and made the interior 3 blocks tall. Without a ceiling on, I can walk through the door at sort of an upward angle. If I place the ceiling tile, then get jammed outside of the doorway... as in I'm too big to fit through the door.

How am I supposed to be able to walk through these doorways if I'm too big to fit?!