Navistar International Corp. said Wednesday (June 20) it adopted a stockholder rights plan, or poison pill, to prevent a hostile takeover of the Lisle, Ill.-based maker of engines, military vehicles and recreational vehicles.

“The plan is designed to deter coercive tactics including the accumulation of shares in the open market or through private transactions and to prevent an acquirer from gaining control of the company without offering a fair and adequate price to all of the company’s stockholders,” Navistar said in a press release.

On June 15, investor Mark Rachesky acquired a 13.6% stake in Navistar, surpassing Carl Icahn as the company’s largest shareholder.

Pursuant to the plan, one preferred stock purchase right will be distributed as a dividend on each share of the company’s common stock held of record as of the close of business on June 29. The plan exempts any person or group owning 15% or more of the company’s common stock as of the time of the first public announcement of the Rights Plan, but only for so long as such person or group does not become the beneficial owner of any additional shares of common stock (including through derivatives).

The rights will expire on June 18, 2013.

Details about the Rights Plan will be contained in a Form 8-K to be filed by Navistar with the U.S. Securities and Exchange Commission.