Crown Holdings has adopted a 10% poison pill, mere days after activist investor Carl Icahn revealed a sizable holding and criticized the beverage-can maker’s structure.

Crown’s board unanimously adopted a one-year shareholder rights plan preventing investors from accumulating a position larger than 10%, according to a Monday morning press release.

Last Thursday, Icahn unveiled an 8.5% stake in Crown making him the second-largest shareholder. Shortly after, Icahn argued at an investor conference that Crown was suffering from a diversified structure and should look to divest non-core divisions and focus on improving its beverage-can business. He also said he was interested in gaining board representation.

Though Crown did not mention Icahn in the press release, it did so in a regulatory filing in which it revealed that the activist last week sent it a notification indicating that he wanted to acquire as much as 20% of the share capital.

Crown shares were slightly up at $75.40 each in midday trading Monday in New York. They were trading close to $130 in March.