Workers at a major Ford Motor Co plant in Ontario are unhappy with a contract their union reached with General Motors Co and would likely vote down a similar agreement, a senior local union official said on Monday.

Ford’s Oakville, Ontario, workers want a more generous deal that would shorten the time it takes new hires to reach the top of the pay grid, said Dave Thomas, president of main Canadian autoworkers union Unifor’s Local 707.

“That framework that GM has set forward won’t ratify in Oakville,” he said in an interview. “My members have huge concerns.”

The local makes up the majority of Ford’s unionized Canadian workforce, giving it a strong influence in a ratification vote.

Unifor has a longstanding practice of “pattern bargaining,” selecting one automaker to negotiate with and then holding the other two to the terms of that deal. It reached an agreement with GM last month.

It is not clear how national union officials could address Thomas’s concerns without deviating from the pattern.

“We’ll deal with Ford when we get there,” said Unifor National President Jerry Dias. “The 707 leadership is listening to their members, and so we’ll see where that takes us.”

Dias said there were always some differences among the automakers, noting that in the last contract, GM was allowed to hire some temporary employees. But he said he remained committed to pattern bargaining.

“Pattern bargaining benefits all of our members,” he said. “Sometimes you’re at the top of the hill, other times you’re at the bottom.”

Any Ford vote is weeks away, as Unifor officials have yet to reach a tentative agreement with the company. The union is currently bargaining mainly with Fiat Chrysler Automobiles NV and has set a strike deadline for Oct. 10.

The GM deal maintained a 10-year earn-in for new hires, while spreading out raises so some workers get pay boosts earlier than before. But the core of the deal was a commitment to invest C$400 million ($305 million) in the GM Oshawa assembly, saving jobs at the plant.

Ford’s bargaining committee is looking for new investment at the company’s Windsor, Ontario, engine plants, but Oakville, which won the new Ford Edge crossover in 2014, does not need new commitments in the short term.

Oakville workers outnumber Windsor’s 5,000 to 1,700 and could reject any deal on their own.