Thailand’s opposition parties are making another attempt to strip the junta-appointed Senate of powers to elect the next prime minister before the national vote likely to be held early next year.

Lawmakers were set to vote late Wednesday on a raft of proposals to amend the 2017 military-backed constitution. A key motion seeks to remove a provision that gives the Senate the power to select the prime minister together with the lower house for the first five years following post-coup elections in 2019.

The proposal is likely to fail to secure more than half of the votes from the combined 750-seat National Assembly. That’s because a third of the 250-member Senate will have to approve the proposed amendment and they were picked by the military that seized power in a May 2014 coup.