The buyback anomaly survives when using the five factor Fama and French (2015) andthe four factor Stambaugh and Yuan (2017) models: buyback announcements are followedby positive long-term excess returns that are positively related to (idiosyncratic) volatility,inconsistent with the low volatility anomaly. The results are consistent with the costly arbitrage hypothesis (Stambaugh et al., 2015) as well as with the market timing hypothesis:the option to take advantage of undervalued stock is more valuable when firm value ismore uncertain or is more driven by company-specific information. Combining volatilitywith undervaluation indicators proposed by Peyer and Vermaelen (2009) improves thepredictability of excess returns after buyback announcements.