Donald Trump wasn't joking when he said he was going to sue Bill Maher for reneging on a bet he made on the Tonight show.

The Donald filed suit Monday in California asking for $5 million -- the amount the comedian said he'd pay the mogul if he could prove he was not the “spawn of his mother having sex with orangutan.”

Monday on Fox News, Trump said, "I don’t think he was joking. He said it with venom... He promised me $5 million for charity if I provided certain information. Well I provided the information. He didn’t pay. So today I sue Bill Maher for $5 million for charity.”

After Maher made the public bet, Trump’s attorney Scott S. Balber released a letter and attached a copy of Trump’s birth certificate. In the letter, Balber wrote, "Attached hereto is a copy of Mr. Trump’s birth certificate, demonstrating that he is the son of Fred Trump, not an orangutan."