According to Musk, paying for Twitter’s whistleblowing is yet another reason to drop the merger.

In a letter to Twitter, the lawyers said Twitter’s failure to seek Musk’s consent before making the Pieter Zatko payment violated the April 25 merger agreement, which limited when Twitter might make such payments.

“This severance … cannot be corrected,” and therefore Musk is under no obligation to complete the merger, the letter states.

A copy of the letter has been filed with the US Securities and Exchange Commission.

Twitter did not immediately respond to a request for comment.

The letter was filed following Musk filed an amended countersuit under seal to incorporate Zatko’s allegations of security lapses at the social media company.