Billionaire Bill Ackman is walking away from a deal announced last month that would have given him a 10% stake in Universal Music Group, the label that is home to Taylor Swift, Billie Eilish, Lady Gaga and the Beatles.

In a letter Monday to shareholders of his investment fund, Pershing Square, Ackman cited questions from the Securities and Exchange Commission about whether the structure of a special-purpose acquisition company would allow such an acquisition under the rules of the New York Stock Exchange.

Vivendi SA last month confirmed that its Universal Music Group was in talks to sell a 10% stake to Pershing's special-purpose acquisition company, or SPAC, in a deal that would value the record label at about $40 billion. The 10% stake would have gone for around $4 billion.

A SPAC is typically a group of larger investors who raise money for acquisitions and then seek out acquisition targets. The deal announced by Ackman last month was unique because unlike a rush of SPACs that have rolled out this year, the intent was not to merge with Universal, but to take a stake in the company that had already announced plans to go public.

On Monday, Vivendi Vivendi said that it had instead approved the acquisition of as much as 10% of Universal by funds associated with Ackman.

Ackman's SPAC, called Pershing Square Tontine Holdings Ltd., now has 18 months left to close a new transaction, unless shareholders vote for an extension. Ackman said that because of the experience with the proposed Universal Music transaction, its next business combination would be structured as a conventional SPAC merger.