Bernie Sanders won his first endorsement from a national union on Monday, becoming the second presidential candidate to do so in the 2020 primary.

The United Electrical, Radio and Machine Workers of America, a 35,000-member union, announced that it is backing Sanders at its convention in Pittsburgh.

The labor organization is a longtime ally of Sanders. It backed him in his first bid for the White House in 2016, and Sanders invited the president of a Pennsylvania-based UE local to speak at his campaign kickoff rally this year. Sanders’ campaign also used its massive email list to push supporters to a UE strike in 2019.

Sanders delivered a speech to the union’s members on Monday before they voted to endorse him, saying corporate greed “is an illness, it is an addiction — and if the corporate CEOs don’t get the treatment that they need, we will provide the treatment for them."

"If there is going to be class struggle in the United States,” he said, "it's time that the working class got on the offensive and won that struggle.”

Former Vice President Joe Biden is the only other 2020 candidate who's received a nod from a national union: the International Association of Fire Fighters, a much larger group with more than 300,000 members.

UE’s endorsement of Sanders comes days after the Vermont senator unveiled his plan to expand organized labor, which envisions ending right-to-work laws and doubling union membership across the country. It also proposes forcing employers of union members to provide to workers the savings they accrue from moving to “Medicare for All.”