Kanye West told President Trump on Thursday that the 13th Amendment was a "trapdoor" through which people "end up next to the Unabomber."

The musician sat across from Trump in the Oval Office and asked, "Why would you keep something around that's a trapdoor?"

West advocates repeal of the post-Civil War amendment, which abolished involuntary servitude but for incarcerated individuals. He visited Trump at the White House to speak about a range of other criminal justice-linked issues.

West said the 13th Amendment was a "trapdoor" where "you'd get locked up and turned into a slave."

"Would you build a trapdoor that if you mess up and you accidentally something happens, you fall and you end up next to the Unabomber? You gotta remove all that trapdoor out of the relationship," West said.

"The Unabomber" is an alias of Ted Kaczynski, an incarcerated domestic terrorist.

[WATCH: Kanye West goes on rant during White House meeting with Trump]

In wide-ranging remarks, West likened his Trump campaign hat to "a Superman cape" and said that he had been inaccurately diagnosed with bipolar disorder. He said he in fact suffered from too little sleep.

West defended his decision to wear the Trump hat that says "Make America Great Again."

"They tried to scare me to not wear this hat," he said. "My dad and my mom separated so there was not a lot of male energy in my home and also I’m married to a family where, you know, there’s not a lot of male energy. It’s beautiful though."

West is married to reality TV star Kim Kardashian West, who visited the Oval Office twice to ask Trump to release a prison inmate. In June, Trump released drug convict Alice Johnson at her urging. She returned in September to request that he release Chris Young, 30, who was arrested at 22 and received a life sentence for dealing drugs.

On Wednesday, Trump told reporters in the Oval Office that "a lot of people" are sentenced to be "locked up for many, many years, and there's no reason for it." On Thursday morning, Trump said in a TV interview, "You have many people like Mrs. Johnson in jail for another 35 years on a charge that -- frankly, everything is serious -- but you don't get life imprisonment because you're talking over a telephone about something."