A Russian immigrant challenged Sen. Bernie Sanders’s version of socialism, asking the 2020 Democrat if his agenda as president of the United States would echo Soviet policies in Russia.

A woman identified as Margaret asked Sanders at a Fox News town hall in Dearborn, Michigan, on Monday, "As someone from Russia, a country that was greatly impacted by the negative effects of socialism, what assurances can you offer myself and other people impacted by socialism that Democratic socialism will not have the same results?"

The Vermont senator responded by denying that the Soviet Union was a socialist country and asserted that real socialism could be found in countries such as Denmark, Finland, and Sweden.

"What happened and existed in the Soviet Union was not socialism. It was authoritarian communism," he replied. "Communism, whether in Cuba, whether in the Soviet Union, whether in other countries, was marked by totalitarianism, was marked by throwing millions of people into the gulag. Stalinism was about as bad as it got."

Sanders, 78, has faced criticism over his past praise for Cuba under dictator Fidel Castro and the Soviet Union after he visited both countries in the 1980s. As mayor of Burlington, Vermont, in 1988, he praised Soviet infrastructure, favorably contrasting it to the U.S.

"There are some things that [the Soviet Union does] better than we do and which were, in fact, quite impressive. Subway systems in Moscow costs 5 kopeks — or 7 cents. Faster, cleaner, more attractive and more efficient than any in the U.S. — and cheap," he wrote in a statement from his office as mayor. "The train trip that we took from Leningrad to Moscow — for Soviet citizens — was very cheap."

Additionally, Sanders took heat for defending Cuba's literacy program under the Castro regime last month.