Editor’s Note: The headline has been updated to clarify that some customers will see a second bill.

OKLAHOMA CITY (KFOR) – As the holidays approach, Oklahoma Natural Gas is advising some customers they can expect to see a second bill this month.

ONG officials say it all revolves around the money you’re charged each month to recover the cost of natural gas ONG purchased during the historic winter storm of 2021.

According to ONG, a system error is to blame. Around 1% of customers (about 10,000 households) weren’t charged for the “winter event recovery cost.”

In an email to those affected, ONG says it’s now sending a second bill for the missed charges.

Company officials say they’re taking steps to ensure the error doesn’t happen again.