KiwiRail says the Cook Strait ferry Arahura had to be taken out of service temporarily because of a crack in its cargo door.
The crack was found on Friday night and has been repaired and approved by Maritime New Zealand.
Two return crossings were cancelled and Kiwirail said services were set to resume at 3pm on Saturday.
However, it is for freight only because of an earlier problem with a lifeboat.
Passengers have to travel on the Kaitaki or the Stena Alegra.