For the second time this year, convicted fraudster Martin Shkreli has filed a jailhouse lawsuit alleging that he himself was the victim of fraud — and this time his target is one of the witnesses who testified against him in his 2017 trial.

In his suit, filed on Friday in Brooklyn federal court, Shkreli says that, in 2007, Lee Yaffe urged his father George Yaffe to plunk down $100,000 to invest in one of Shkreli’s hedge funds, Elea Alpha.

When Shkreli lost the money, the younger Yaffe talked Shkreli into giving his father a $250,000 promissory note.

“Man up,” Lee Yaffe allegedly told Shkreli, according to the suit.

Shkreli, 36, gave George Yaffe the IOU — but he ended up welshing on it.

George Yaffe sued him last year in Manhattan Supreme Court. Shkreli, who is doing a seven-year stint in a federal prison in Allenwood, Pennsylvania, never responded to the lawsuit — thus, the judge in the case ruled in George Yaffe’s favor and ordered Shkreli to pay the promissory note plus interest, bringing the total to $420,000.

In his new federal suit, in which he claims that Lee Yaffe defrauded him into issuing the IOU, Shkreli says that he’s under no obligation to make good on the promissory note.

Under New York state law, Shkreli alleges, a promissory note isn’t valid unless it’s for a debt.

An attorney for George Yaffe did not immediately respond to a request for comment.

In May, Shkreli sued three people connected with the pharmaceutical company he created, who he says ripped him off to the tune of $30 million. That case was settled less than a month later.

Debra Guzov, who represents George Yaffe in the Manhattan case, called Shkreli’s suit “frivolous” and said it is an effort to get out of paying the judgment against him.

“All along, Shkreli has been stonewalling us to stop us from enforcing the judgment against his assets,” she said.

Edward Kang, Shkreli’s Philadelphia-based attorney in his lawsuit, said the suit isn’t about revenge against a witness against him and that his client has “moved on from the criminal case.” Kang declined to address Guzov’s characterization of the suit.

“We will let the court system play out, where we believe Mr. Shkreli’s rights will be vindicated,” he said.