(RALEIGH) -- A proposed constitutional amendment narrowly advanced through the North Carolina House thanks to an accidental supporter.

The House approved a measure that would prevent lawmakers from serving more than four years as House Speaker or Senate President Pro Tempore. The legislation cleared by a vote of 72 to 47, exactly the threshold needed to pass a constitutional amendment.

Rep. Jean Farmer-Butterfield, D-Wilson, originally opposed the bill during the first of two required votes.  However, she mistakenly voted for the measure the following day. Lawmakers are allowed to change their vote, unless it changes the outcome. Farmer-Butterfield wasn’t immediately available to comment, although the accidental vote was confirmed by House Minority Leader Rep. Joe Hackney.

Many House Democrats objected to the proposed amendment, citing concerns that it would put the legislative branch at a disadvantage to the executive branch. Opponents also said leadership term limits would be better addressed through statute, not by changing the state's constitution.

The legislation now heads to the Senate, where Republicans have larger majority. Senate president Phil Berger, R-Rockingham, has also been a vocal supporter of term limits.