During a recent appearance on The Late Show with Stephen Colbert — available on YouTube — Democratic presidential frontrunner Joe Biden spoke about everything from his recent string of gaffes to his thoughts on Donald Trump’s administration. He also addressed the purported technology-driven “fourth industrial revolution” and the development of self-driving trucks, two issues that are central to fellow candidate Andrew Yang’s campaign.

“We’re in the middle of something else going on here, nothing to do with Donald Trump. We’re in the middle of what I call — other people call — the fourth industrial revolution,” he said.

Biden went on to describe his fear of losing the middle class and highlighted the retail job losses due to Amazon, as well as the purported threat the truck driving industry faces due to the development of self-driving trucks.

Yang’s campaign is centered around a universal basic income (UBI) of $1,000 per month for every American funded by taxing big tech companies like Amazon, Google, and Facebook. His proposal seeks to provide a cushion for Americans in the midst of what experts call the fourth industrial revolution, which Yang believes is pushing more and more Americans to the sidelines, primarily due to automation.

But while Biden spoke of similar problems, his solutions differed. Notably, he proposed job training, which Yang frequently addresses in his campaign and claims is not the right solution due to low success rates.

Here's Joe Biden talking about what he calls the Fourth Industrial Revolution, self-driving trucks, and how we're going to need policies like job training and Pre-K for low income school districts to get through it... #YangGang #Yang2020 pic.twitter.com/ytxRfS2UhH — Scott Santens (@scottsantens) September 5, 2019

It’s not the first time Biden has expressed concern with Yang’s ideas. The San Francisco Chronicle reported that the Democratic front runner spoke to Yang about these issues during a commercial break of the first round of Democratic debates.

“No matter what happens, Andrew, you and I need to sit down and talk about the fourth industrial revolution because I’m terrified that we’re going to gut the middle class,” Yang recalled Biden saying to him.

According to Yang, Biden’s interest during the debate was a “very, very positive thing” and a sign that his message is getting through to all kinds of Americans.

Despite some agreement, the pair don’t agree on everything. On a recent appearance on CBS This Morning, Yang was critical of Biden’s campaign and its focus on restoring the legacy of Barack Obama. Yang claims that a Biden presidency with such a focus would take America a step “backwards in time” — not forward.

“And so to me, saying that we can somehow erase not just Donald Trump’s presidency, but all of the reasons why people voted for Donald Trump, to me is not correct.”

Per RealClear Politics, Biden is currently in first place in the Democratic presidential primary with 30.1 percent support, while Yang is in sixth with 2.6 percent support.