We investigated thematic processing in sentences containing a prepositional phrase that was ambiguous between a locative and a temporal interpretation. We manipulated context (temporal or locative), target sentence (temporal or locative), and whether or not the main verb of the target and the context was repeated. Results showed that context dictated the participants' thematic expectations. Thematically, congruent target and context pairs were read faster than incongruent pairs. This effect was not modulated by verb repetition. We argue that wh -words cause readers to lodge semantically vacuous thematic roles in their discourse representation that bias a reader's interpretation of subsequent thematically ambiguous adjuncts in their discourse representation.