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We now know why "Saved by the Bell" star Dustin Diamond did to allegedly violate his parole last month: He failed a drug test.

It was revealed on June 10 that Dustin, who starred as the infamous "Screech" in the beloved 90s sitcom, tested positive for the painkiller Oxycodone during a routine test in May.

In documents unearthed by TMZ, Diamond told his parole officer he'd recently taken "a painkiller" for a toothache, but he also admitted that he didn't know what that specific painkiller was because it was an old prescription.

That violation put Dustin behind bars on May 25 for two days.

The website said he told cops he's now "cleaned out" his medicine cabinet.

At the time of the arrest, Dustin had only been out of Wisconsin jail for about 6 weeks, having served three out of the four months after being sentenced to prison for a bar stabbing on Christmas Day in 2014. He had been charged with carrying a concealed weapon and disorderly conduct.

Authorities said Dustin's girlfriend got into an altercation with another woman who was antagonizing the couple at the bar. It eventually turned physical and Dustin began defending his girlfriend, which is when he pulled out a switchblade knife.

On May 17, in between his jail release and his two-day jail stay, he gave his version of what happened to "Extra" co-host and his old co-star Mario Lopez.

"I opened my pocket knife and said, 'Let my wife go immediately,' which worked," he said. "I had my pocket knife like this... and the blade was right here and the guy came from around me and grabbed my throat, and so he nicked his arm on the tip of it -- it was a Band-Aid, the most expensive Band-Aid I've ever bought."

He also said he was ready to move on.

"I want to put the tomfoolery and malarkey behind me … for that clean slate," he said, "time for a change."

Dustin didn't have many good things to say about his time behind bars, so it was a surprise that he found himself back there so soon last month.

"It's pretty daunting," he said of jail. "It's pretty scary going into that environment. I found that as long as you follow the rules and stay with the system, it works. You can get in and out unscathed."