We investigate the impact of corporate diversification on stock risk. For identification, we exploit an exogenous shock on volatility expectations related to COVID-19 lockdowns resulting in a period of high volatility. We show that firms that diversify only internationally experience a lower post-shock increase in daily volatility. However, diversifying only by business segment leads to a higher increase in post-shock daily volatility. Our main results are robust to different proxies for international and business diversification and daily volatility. Overall, these findings provide a more nuanced picture of the potential impact of corporate diversification on stock risk.