Striking Boeing workers in the United States are set to vote on a new contract deal after a previous offer by the company failed to get them back to work.

The offer to be voted on Monday includes a 38 percent pay rise over four years, a $12,000 ratification bonus and the reinstatement of an annual bonus scheme that was not included in the earlier proposal, The International Association of Machinists and Aerospace Workers (IAM) said in a statement on Thursday.

Nearly two-thirds of workers last week rejected a contract that would have provided a 35 percent wage rise over four years but did not restore a defined pension plan sought by many employees.

Workers have been pushing for a 40 percent wage increase and the reinstatement of the old pension scheme.

“Your union is endorsing and recommending the latest IAM/Boeing contract proposal. It is time for our members to lock in these gains and confidently declare victory,” the IAM chapter said.

Some 33,000 IAM members have been on strike since September 13, halting operations at Boeing factories in the Seattle area that produce the 737 Max and 777.

The strike has added to a difficult year for Boeing, which has been under intense scrutiny since a January incident during which a 737 Max plane operated by Alaska Airlines lost a door panel midflight.

Boeing shares rose 2.5 percent in after-hours trading after the announcement of the latest offer, after closing 3.2 percent earlier on Thursday.