ST. LOUIS (AP) — A quirk in the mail delivery system that forced some rural Missouri residents living along the Iowa and Arkansas borders to have mailing addresses in neighboring states has been fixed, U.S. Sen. Claire McCaskill said Tuesday.

The idiosyncrasy affected just a few people but created problems and red tape when they voted, paid taxes and even when they died.

McCaskill learned about the oddity last year and began inquiries to the U.S. Postal Service. In a letter to McCaskill on Monday, Postmaster General Megan Brennan wrote that the issue has been resolved and those who previously suffered from border confusion can now use Missouri as their state designation.

Brennan said the conversion has actually been in place for several months without any reported problems.

McCaskill, in a statement, said she was glad “we’ve made progress in fixing this bizarre and inconvenient quirk once and for all.”

McCaskill, a Democrat, serves on the Homeland Security and Governmental Affairs Committee, which has jurisdiction over the Postal Service. She is running for re-election against Republican Missouri Attorney General Josh Hawley.

The exact number of affected residents was unknown. Also unclear is why Missouri residents were assigned Iowa and Arkansas postal addresses in the first place.