SpaceX delayed a critical test flight of its massive Starship rocket roughly half an hour before liftoff on Sunday, saying it needed to fix a liquid oxygen leak and that it would aim for another launch on Monday night.

SpaceX crews are preparing for the 10th flight test of its Starship spacecraft and Super Heavy rocket. The launch is currently set for 7:30 p.m. from SpaceX’s Starbase launch facility in Texas. Monday’s flight attempt comes after SpaceX scrubbed its planned launch on Sunday due to ground systems issues.