Washington (CNN) Former Trump campaign aide Sam Nunberg said Wednesday he warned Roger Stone about associating with WikiLeaks founder Julian Assange, whose organization released hacked Democratic emails during the 2016 election.

"I warned (Stone) repeatedly during the 2016 summer, do not associate yourself with Julian Assange," Nunberg said in an interview on CNN's "New Day."

When asked how Stone, a longtime adviser to President Donald Trump, responded to his warnings, Nunberg said, "Roger is going to do what Roger is going to do."

"Roger's advised me not to do certain things. We're very stubborn people," he said of the man he calls his mentor

Stone, who briefly served as a Trump campaign adviser early in the race, is a subject in the special counsel's investigation, Nunberg told CNN last week.

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