Christina Hammock Koch

NASA canceled the first all-female spacewalk because of a lack of medium-sized space suits.

The space agency said Monday that it was canceling its first all-female spacewalk, originally scheduled for March 29.

The spacewalk wasn’t going to be a “historic” mission (meaning there would have been no official ceremony around it), but it would have represented a monumental shift in the agency — and it would have happened during Women’s History Month. Astronauts Christina Koch and Anne McClain were scheduled to make the walk and the support team would have been all female, too.

But last week, McClain went for her first spacewalk and “following the first spacewalk, mission managers decided to adjust the assignments, due in part to spacesuit availability on the station,” according to a statement. “McClain learned during her first spacewalk that a medium-size hard upper torso — essentially the shirt of the spacesuit – fits her best.”

Apparently, only one medium-sized spacesuit can be made ready by the scheduled Friday walk. And Koch is the one scheduled to wear it.

Aboard the International Space Station, there are two large torsos and one extra-large torso suit ready, Quartz reported. (Plus one spare extra large.)

“We do our best to anticipate the spacesuit sizes that each astronaut will need, based on the spacesuit size they wore in training on the ground, and in some cases astronauts train in multiple sizes,” NASA spokesperson Brandi Dean told Quartz. “However, individuals’ sizing needs may change when they are on orbit, in response to the changes living in microgravity can bring about in a body.”

This Friday’s mission will still take place as regularly scheduled, just with one new astronaut. (Astronaut Nick Hague will be McClain’s replacement.) The two astronauts will step outside of the International Space Station on a six-hour mission to install

McClain is scheduled to make her next spacewalk on April 8.

Both spacewalks will still be broadcast by NASA.

After her walk last week, McClain became the 13th woman to walk in space. Koch will become the 14th when she steps foot out of the International Space Station on Friday.