Invalid votes are often considered as simple failure to cast a valid vote. In fact, they might be a rational expression of discontent with party policy offerings. By employing individual and party system-level data on eighteen European party systems, this article focuses on voter discontent and voter apathy as two major determinants of casting an invalid vote and seeks to answer why some voters intentionally waste their votes despite paying the costs of voting. I find that higher distinct policy offerings decrease the probability of casting an invalid vote. However, voting behaviors of politically sophisticated and unsophisticated voters vary conditionally on the diversity of policy offerings and the cost of information. On one hand, when a party system offers a larger set of policy offerings, politically sophisticated voters become less likely to cast an invalid vote and more likely to support niche parties. On the other hand, sophisticated voters cannot deal with increasing cost of information, and are more likely to cast an invalid vote, especially in party systems with compulsory voting where the cost of nonvoting is higher.