New York City’s bike share program abruptly announced on Friday evening that it would shut down for the weekend to improve the service.

Citi Bike sent an email to members around 5 p.m. saying that the system would close at 10 p.m. on Friday. The email apologized for the short notice and explained that service was being suspended for maintenance “to make the system more reliable.”

“We have been hard at work all winter to prepare improvements to Citi Bike, and we are doing everything in our power to put them in place in advance of the peak riding months,” the email said.

The shutdown is the first time the entire bike share program has closed for a weekend since the service, under which people rent bikes and ride them between stations around the city, began in 2013. The criticism on Twitter was swift as riders complained about the sudden decision and of having to rearrange weekend plans.