(The Hill) — Sen. JD Vance, R-Ohio, received some heckling and boos while speaking at a firefighters union event Thursday in Boston.

Vance delivered remarks at the International Association of Fire Fighters conference. Upon taking the stage after Rep. Carlos Gimenez, R-Fla., a former firefighter, Vance drew some boos from the crowd. 

“Semper fi, guys,” Vance said, the abbreviation for the Latin phrase and Marine Corps motto “Semper fidelis,” which means “always faithful.”  

“We got some — it sounds like we got some fans and some haters. That’s OK,” Vance said in response to the reaction. “Let’s listen to what I have to say here, and I’ll make my pitch.”   

The Ohio senator praised the firefighters and thanked them for their service in his speech, saying, “you make a difference every single day, and I thank you for it” and vowed that the Trump campaign “will always stand with the courageous firefighters and the first responders who keep this country safe every single day.” 

Vance also sought to highlight his support around related legislation, such as co-sponsoring the Social Security Fairness Act and for voting in favor of the Fire Grants and Safety Act.  

The Ohio senator received boos at another point in his speech moments after he argued that the Trump-Vance ticket was the “most pro-worker Republican ticket in history.”  

At the same time, Vance also received applause from the crowd at various points, including when he said Republicans would defend peoples’ right to free speech, “including your right to speak out about unconstitutional COVID vaccine mandates.”

He also drew applause from saying that a Trump White House would respect workers’ rights to engage in collective bargaining and for his mention of Corey Comperatore, the volunteer firefighter who died during the attempted assassination against Donald Trump in Butler, Pennsylvania. 

The Ohio senator acknowledged the contrasting reactions in his speech, noting he was once a skeptic of the former president himself. 

“Now I know this is a diverse union. Some of you love President Trump, and some of you clearly don’t,” Vance said, noting: “I’ve heard from both sides.”

“Now this may come as a shock to you, but once upon a time, I wasn’t a Trump guy either, and trust me, the president never lets me forget it,” he added.

“I’ll tell you, whatever your politics and whatever your preferences, I make this solemn promise, whether you support us or not, whether you ultimately endorse us or not, President Trump and I believe in our firefighters, we believe in our first responders, and we will never stop fighting for you,” Vance said toward the end of his speech.

The Trump campaign and some Republicans praised Vance on X for campaigning in Boston, a traditionally blue stronghold. Democratic vice presidential nominee Minnesota Gov. Tim Walz campaigned in front of the same conference Wednesday.