Nuance Communications, a maker of speech-recognition software, rose in extended trading after billionaire investor Carl Icahn disclosed a 9.3 percent passive stake in the company.

The shares advanced 8.3 percent to $21.85 after hours. Nuance had dropped 9.6 percent this year through the close of regular trading yesterday.

Nuance disclosed the stake in a regulatory filing.

Icahn, 77, is ranked 36th on the Bloomberg Billionaires Index, with a net worth of $19 billion.