Earlier this summer, the Google Self-Driving Car Project put an autonomous Lexus SUV to the test on the streets of Austin, Texas, where they hoped to try it against the city’s many cars, pedestrians and cyclists. But recently, one cyclist managed to totally confuse one of Google’s prototype self-driving cars while waiting for his turn to cross the street.

According to a cyclist’s post in an online forum, he ran across the self-driving car at a four-way stop sign while riding his fixed-wheel bike. The car beat him to the intersection and had the right of way, so the cyclist decided to do a maneuver called a track stand. But as Matt McFarland writes for The Washington Post, this common trick sent the computerized car into something like a nervous meltdown.

The cyclist described the experience on a forum called Road Bike Review:

It apparently detected my presence … and stayed stationary for several seconds. it finally began to proceed, but as it did, I rolled forward an inch while still standing. The car immediately stopped… I continued to stand, it continued to stay stopped. Then as it began to move again, I had to rock the bike to maintain balance. It stopped abruptly.

Google’s autonomous cars are programmed to be careful in the extreme as the company’s engineers try to prepare the vehicles for every possible scenario they might come across on the open road. But even though the cars are programmed to recognize cyclists in motion, a track stand managed to confuse the onboard computer to the point where it essentially froze in the middle of an intersection for almost two minutes, the cyclist wrote.

According to McFarland, the issue stemmed from how cyclists rock back and forth while performing track stands. Cyclists often use the maneuver while stopped at an intersection, balancing and rocking the bike back and forth while refraining from taking either of their feet off of the pedals. But while a human driver might be able to tell that the cyclist won’t zip out in front of them, it appears that the driverless car wasn’t able to predict what was going to happen.

While Google’s safety tests have included people throwing beach balls at driverless cars and having humans jump out of bags, it seems that they didn’t prepare it for this particular behavior, Kelsey Campbell-Dollaghan writes for Gizmodo. However, according to Google’s accident reports, autonomous cars were only involved in 12 minor accidents over six years of testing, all allegedly due to human drivers.

In the meantime, Google is going full-steam ahead with its Austin-based tests: while the trials started out with Lexus RX450h SUVs modified to be driverless, the company is introducing its prototype driverless cars to Austin's streets. If the tests are successful, it might be just a matter of time before they start appearing in other cities, with new cyclists ready to test the cars’ reaction time.

An earlier version of this article stated that Google would not have test drivers in their prototypes. The test vehicles will have drivers in them. We regret the error.