With no buyer in sight, bookseller Borders Group has been forced to give an activist hedge fund an bigger say in its future.

The Ann Arbor, Mich.-based company issued warrants for 5.15 million shares to Pershing Square Capital Management, already its largest shareholder with a nearly 29% stake. As part of a March agreement under while Borders hung out a “for sale” sign, without a deal to sell or restructure by Wednesday, the chain had to issue the $7 warrants, which are valid for six years.

Borders runs more than 1,100 stores, and Ackman has been pushing a possible deal with online bookseller Amazon.com.