Philosophers traditionally held that knowledge is justified true belief. Gettier (1963) challenged this view with thought experiments in which someone has a justified and true belief, but an element of luck is involved that disqualifies the belief from counting as knowledge. We examined laypeople’s concept of knowledge using a semantic integration paradigm modeled after that of Gentner (1981). Participants read stories in which a character ‘thought’ something was true. On a subsequent recall task, readers sometimes falsely recalled the verb ‘thought’ as ‘knew,’ implicitly indicating that the reader had attributed knowledge to the character. False recall of ‘knew’ occurred more frequently when the story described a justified true belief than an unjustified belief. Justified true belief triggered these recall errors even in a so-called “Gettier case”. The present findings suggest that semantic integration provides an empirical paradigm suitable for investigating lay notions about knowledge.