The Occidental Petroleum Corp. (Oxy) board on Friday adopted a limited duration stockholders rights plan, known commonly as a “poison pill,” in an effort to dilute activist billionaire shareholder Carl Icahn’s growing stake in the Houston-based independent.

The rights plan “is intended to enable all stockholders to realize the long-term value of their investment in Occidental,” said Vice Chairman Jack Moor. “We adopted the rights agreement to protect stockholders from efforts to capitalize on recent market volatility and macroeconomic conditions to gain control of the company without paying all stockholders an appropriate premium for that control.”

Icahn, a vocal opponent of Oxy’s $57 billion acquisition of Anadarko Petroleum Corp. has called for the firing of Oxy CEO Vicki Hollub. Icahn revealed last week to the Wall Street Journal that he had increased his stake in Oxy to just under 10%, taking advantage of plummeting North American exploration and production stocks amid the Russia-Saudi oil price war, and a bearish demand outlook from the coronavirus pandemic.

The rights plan, to be voted on by Oxy shareholders at the 2020 annual meeting, would authorize a dividend of one “right” for each outstanding share of Oxy common stock. Rights will be issued at the close of business on March 23. Oxy typically holds its annual meeting in May.

The rights can only be exercised if a person or group acquires 15% (or 20% in the case of passive institutional investors) or more of common stock in a transaction not approved by the board, the company said.

If Oxy’s board approves the agreement, the rights would expire on March 11, 2021.

In a scathing Feb. 12 open letter to fellow Oxy stockholders, Icahn accused Hollub and Chairman Gene Batchelder of recklessly engaging in a bidding war with Chevron Corp. to acquire Anadarko in an “ill-advised bet that has already destroyed over $30 billion in stockholder value…”

Icahn alleged the reason they did so was that they and the rest of the board “were fearful that Oxy would be acquired. We believe they were focused on protecting their jobs and viewed the Anadarko transaction as a defensive maneuver that allowed Oxy” to be the acquiring company rather than being acquired itself.

Oxy reported a 4Q2019 net loss of $1.34 billion (minus $1.50/share), versus net profit of $706 million (93 cents) in the similar 2019 period.