As we marked Yom HaShoah (Holocaust Remembrance Day) this week, parties to the 2015 Iran nuclear deal began talks toward seeing America and Iran return to the accord.

It remains crucial that the Iranian regime, which seeks to finish Hitler’s work with its declared desire to eliminate the Jewish state of Israel, be held accountable for its denial of the Holocaust. Don’t take my word for it. Take Iran’s.

In 1998, former Iranian President Ali Akbar Hashemi Rafsanjani opened a rally to commemorate Al-Quds (Jerusalem) day by labeling the fact that 6 million Jews were killed in the Holocaust as “Zionist propaganda.”

In early 2001, writers for the government-run Tehran Times offered falsehoods about the Holocaust, with one saying that just 150,000 prisoners died at Auschwitz (at least 1.1 million prisoners died at the concentration and death camp) and that most deaths were due to disease. Another writer claimed that there’s no proof “even one human being in a German camp” was gassed. The writer added that German documentation “directly refute” the “Holocaust story” (even though there is overwhelming proof, even from German documents at the time, that proves that the Holocaust happened).

The following April, Iranian Supreme Leader Ayatollah Ali Khamenei told a conference in Tehran that “exaggerated numbers” of Jews killed during the Holocaust were “fabricated to solicit the sympathy of world public opinion, lay the ground for the occupation of Palestine, and justify the atrocities of the Zionists.” In January 2005, the Tehran Times ran a piece by Hossein Amiri titled “Lies of the Holocaust Industry.”

The following December, then-Iranian President Mahmoud Ahmadinejad remarked, “Some European countries are insisting on saying that Hitler burned millions of oppressed Jews in crematoria. They insist so much on this issue that if someone proves the opposite, they convict him and throw him into prison.” In his 2014 new year speech, Khamenei said that “the Holocaust is an event whose reality is uncertain, and if it has happened, it’s uncertain how it has happened.”

In December 2015, a $50,000 cash prize for the best cartoon about the Holocaust was announced by the 11th Tehran International Cartoon Biennial. The event was held in May 2016 and featured 150 Holocaust cartoons. The exhibition started on May 14, also the 68th anniversary of Israel’s independence. Last October, Khamenei tweeted, “The next question to ask is: why is it a crime to raise doubts about the Holocaust? Why should anyone who writes about such doubts be imprisoned while insulting the Prophet (pbuh) [Mohammed] is allowed?”

There are many other instances of Iran’s Holocaust denialism. This matters. Holocaust historian Deborah Lipstadt said, “There are facts; there are opinions, and there are lies.” The Iranian regime is rooted in lies. That includes its denial of the darkest period in human history.

A rallying cry of Holocaust remembrance is “Never forget.” We must never forget that the Iranian regime denies the Holocaust while seeking to annihilate the Jewish state. To that, we say, “Never again.”