A planned committee vote on the Senate Republican tax bill Tuesday afternoon is in doubt after a key Republican member of the panel demanded Tuesday morning that the bill get a major change before he votes for it.

“We do need to have this trigger issue worked out before the budget vote today,” Tennessee Sen. Bob Corker said in an appearance on Fox News, referring to a provision he wants added to the bill that would lessen some of its tax cuts in the case the federal debt rose too fast.

The Budget Committee is scheduled to vote on the Tax Cuts and Jobs Act at 2:30 p.m. Republicans have a one-vote majority on the panel, meaning a “no” vote from Corker would stop advancement.

Another Republican on the panel — Sen. Ron Johnson, of Wisconsin — has suggested he could vote against committee passage unless changes are made to increase the tax cuts given to small businesses in the bill.

The committee vote is not supposed to include amendments. Rather, it is a procedural step for moving along the bill, which Republicans are trying to pass through the budget reconciliation process that would allow them to bypass any Democratic filibuster. Corker said Monday the committee action was “not particularly important.”

Senate leadership has said they aim to begin voting on the bill on the Senate floor on Wednesday and pass it by Friday. That timeline would keep it on track for passage by the end of the year.

Republicans said Monday they were aiming to change the bill to try to shore up support among hesitant members of their conference.