After billing less than $20 million in hourly fees for its representation of Twitter in M&A litigation against Elon Musk last year, Wachtell, Lipton, Rosen & Katz asked for and received an additional success fee in excess of $70 million in the final hours before the deal closed, a Wednesday complaint against Wachtell alleges.

The lawsuit, filed by Reid Collins & Tsai on behalf of Twitter parent company X Corp in California Superior Court in San Francisco on Wednesday, alleges Wachtell’s request for the success fee from Twitter’s “lame duck” outgoing in-house counsel violated the firm’s legal and ethical duties to its client. Twitter is asking for the fee agreement to be voided and the success fee disgorged.