More than 1,000 donors to the American Civil Liberties Union (ACLU) made contributions to the organization in the spring but only recently were alerted to the fact that their donations were not processed.

In a letter to affected donors, ACLU Director of Development Operations Veronica Koo explained that a donation in April was received but never deposited due to an error at the bank but the nonprofit only learned of the mistake months later.

The bank showed that the check was deposited and then recognized but that never actually happened, Koo said. “Since discovering the issue, BB&T bank has updated procedures to ensure that this issue will not occur again,” she said in the letter to donors. The error affected about 1,200 donors who mailed checks in April.

ACLU received checks at its lockbox, which scans them electronically, and they showed as having been deposited and reconciled, she said. Normally, once a donation is received, ACLU turns it around in 48 hours. “It took a while for us to find out about the error within the bank’s IT department,” Koo said, and then the approximately 1,200 donors had to be hand-checked into the system for the follow-up mailing, which was dated Oct. 30.

It’s not clear yet how many donors have re-upped their donations, Koo said, but some had called to inquire about its status while others had already made another gift to make up for the first one. In her letter to donors, Koo apologized for the error and inconvenience and provided instructions for those who wanted to re-up their gift. She declined to reveal the aggregate monetary sum that would have been received from the 1,200 donors.

Koo said it was the first time something like that had happened in her nearly 10-year tenure with the New York City-based organization.

The ACLU and other nonprofits backing progressive causes have seen a surge of donations in the past year in response to moves by the Trump Administration. ACLU reported almost $35 million in donations after President Donald J. Trump’s executive order in January banning those from seven predominantly Muslim countries from entering the United States. In the months after the November 2016 election, ACLU saw its membership double to 1 million and its followers on Facebook and Twitter grow by some 150 percent and 200 percent, respectively.