The hedge fund manager said his fund began buying Uber shares in early January and has amassed 30.3 million shares, worth $2.3 billion.

Uber stock hit its highest level since October after Ackman disclosed his Pershing Square hedge fund accumulated a 1.4% stake in the ride hailer.

Bill Ackman said his hedge fund Pershing Square Capital Management owns 30.3 million shares of Uber Technologies Inc., citing the strength of the rideshare company’s management and saying that its stock is undervalued.