The development of Boeing’s new crew-carrying space capsule, the CST-100 Starliner, hit a roadblock last month. The company experienced an undisclosed “anomaly” in June when conducting a test of the Starliner’s launch abort engines — the key hardware that could help save the spacecraft in case of an emergency. Boeing says it has figured out what went wrong, but it’s unclear if this will delay the first milestone flights of the vehicle moving forward.

The Starliner is the spacecraft that Boeing has been developing over the last decade as part of NASA’s Commercial Crew Program. It’s designed to take the space agency’s astronauts to and from the International Space Station, though the vehicle’s launch abort engines are manufactured by Aerojet Rocketdyne. These small engines are embedded inside the Starliner’s service module, a cylindrical structure that sits underneath the capsule during launch to provide support. If the rocket carrying the capsule were to suddenly malfunction on the launchpad or after takeoff, the engines would fire, propelling the Starliner and its passengers away to safety.

Both Aerojet and Boeing have conducted hot-fire tests of the engines, during which the hardware is ignited on a test stand to see if it’s working properly. As first reported by Ars Technica, Boeing was doing another one of these tests last month at NASA’s White Sands Test Facility in New Mexico when some kind of mishap occurred. The engines ignited and fired during the full test, according to Boeing, but when they shut down, something caused a propellant leak.

Boeing says it has a fix for what happened, though. “We have been conducting a thorough investigation with assistance from our NASA and industry partners,” the company said in a statement. “We are confident we found the cause and are moving forward with corrective action. Flight safety and risk mitigation is why we conduct such rigorous testing and anomalies are a natural part of any test program.”

The company did not provide any updates on how this might affect the Starliner’s testing schedule moving forward. Boeing and NASA’s other Commercial Crew partner, SpaceX, are currently slated to launch their vehicles for the first time, without crews, sometime in August, followed by crewed missions by the end of the year. But before Starliner flies with crew, Boeing plans to do a pad abort test, where the launch abort engines will be tested on a Starliner capsule. That test is supposed to happen by the end of the summer, according to Space News.

However, this latest setback comes amid wide speculation that Boeing and SpaceX will not meet their scheduled deadlines for launching their vehicles. The Government Accountability Office has released multiple reports claiming that the current schedule is too aggressive, and the first crewed flights of the two vehicles will possibly move to 2019. August is around the corner, though, and there’s a possibility that NASA will have some kind of ceremony at the beginning of the month to announce new dates for the Commercial Crew flights, according to Orlando Weekly. So it’s likely that NASA will provide some update on scheduling soon.