Florida’s historic recount was thrown once more into uncertainty Thursday when a federal judge ruled that voters whose mail-in and provisional ballots were rejected because of issues with their signatures will have two more days to resolve the problems and possibly have their votes counted.

The decision by Judge Mark Walker of the U.S. District Court in Tallahassee came just hours ahead of the Thursday afternoon deadline for elections officials to complete a machine recount. It is particularly notable in the too-close-to-call Senate race, in which Gov. Rick Scott (R) leads Sen. Bill Nelson (D) by fewer than 13,000 votes.

Walker’s decision affects Floridians who cast their ballots by mail, or voted provisionally, but whose signatures did not match records maintained by state officials. More than 4,000 ballots across 45 counties in Florida were set aside because of inconsistent signatures, he wrote in his opinion. In the other 22 counties, the number is unknown.