The SEC has filed a lawsuit against Elon Musk over his failure to disclose his acquisition of Twitter on time.

The Securities and Exchange Commission sued Elon Musk on Tuesday over alleged securities violations related to his acquisition of Twitter, now called X.

The SEC alleges that Musk failed to timely disclose his 5% Twitter ownership stake, violating federal securities law, according to a complaint filed in federal court in Washington, D.C. The SEC alleges that Musk waited to disclose the acquisition in order to build a larger position in Twitter at a discount.

This lawsuit comes during Gary Gensler’s final week as SEC Chairman, before he steps down on January 20. Gensler and Musk have had some run-ins over the past four years, including just last month when Musk mocked the SEC’s settlement offer for X. However, Musk may face a friendlier SEC commissioner in a few weeks when Trump’s nominee takes office.

The SEC complaint says Musk disclosed his Twitter acquisition 11 days late. After purchasing more than 5% of Twitter — which Musk allegedly did on March 24, 2022 — he was required by the Securities and Exchange Commission to file a report on beneficial ownership. The report was filed on April 4, 2022, according to the SEC complaint.

During this late disclosure period, Musk allegedly increased his position in Twitter from a 5% stake to a 9% stake. On the day Musk revealed his acquisition to the SEC, Twitter’s stock price rose 27% compared to the previous day’s closing price. The SEC claims this allowed Musk to underpay for his Twitter stake by more than $150 million.

In its complaint, the SEC suggested that Musk return the profits he unfairly received and pay an additional civil penalty. Ultimately, a federal court will decide whether the SEC’s allegations have merit and determine whether Musk should be fined.

Musk’s lawyer, Alex Spiro, called this complaint an “admission” that the SEC cannot bring an “actual case,” in a statement to Bloomberg Tuesday.

“With the SEC backing down and leaving office, the SEC’s multi-year harassment campaign against Mr. Musk has culminated in a single complaint against Mr. Musk,” Spiro told Bloomberg.

In a December post on X, Musk shared a message from Spiro communicating with him Similar remarks also point to “years of harassment” from the SEC. That letter rejected the settlement offer from the SEC on the case.

Replacing Gensler is President-elect Donald Trump Nominated by Paul Atkinswho served as SEC commissioner during the Bush administration and is expected to be friendlier to Trump’s allies. These days, Musk is as close to Trump as anyone, and the owner of X could face a different regulatory regime in a few weeks.