A SpaceX Starship rocket exploded during a test over the weekend, marking the second such failure within four months for Elon Musk’s rocket company.

The prototype appeared to blow up during the Friday evening test at SpaceX’s facility in Boca Chica, Texas, sending its top half flying into the air before it crashed to the ground. The rocket was filled with liquid nitrogen fuel for the failed “cryo proof test,” according to the blog NASASpaceflight, which published footage of the incident.

Musk, SpaceX’s founder and CEO, bemoaned the failure on Twitter but vowed to press on with the Starship, which aims to eventually carry people to Mars.

“So … how was your night?” Musk tweeted early Monday as he shared video of the botched test.

“It’s fine, we’ll just buff it out,” he added.

Musk attributed the failure to a “puck” at the base of the rocket that absorbs the “thrust load” from the engine. He said SpaceX would strip the next Starship prototype to the “bare minimum” and test the puck under pressure.

An earlier version of the Starship reportedly exploded during a failed pressurization test in November. That failure was “not completely unexpected” because the test aimed to “pressurize systems to the max,” a SpaceX spokesperson told CNET at the time.