William Ackman’s activist hedge fund Pershing Square Capital Management has upped its stake in Borders Group to 17.1%, according to a Securities and Exchange Commission filing Friday.

In the filing, Pershing Square reported owning roughly 10.1 million shares of the giant bookseller. In an earlier SEC filing submitted on Oct. 9, the hedge fund reported owning 6.9 million shares of Borders, which then amounted to an 11.7% stake.

Ackman has reportedly been solicited by the board of the bookseller for his views of the firm’s management. In the past, Ackman has discussed the makeup of the board and corporate governance issues in general with Borders. It is not known if his latest interest in the firm is an attempt to agitate for change.

Ackman is well known in both hedge fund circles and the corporate world for shaking up management at companies such as McDonald's Corp. and Wendy's International.