Self-derivation through integration is the process of integrating novel facts and producing new knowledge never directly taught. Knowledge integration has been studied with the presentation of two novel facts. However, in educational settings, individuals are required to integrate new information with prior knowledge learned days, months, or years earlier. Prior knowledge robustly predicts learning outcomes, but less is known about self-derivation through the integration of new information with prior knowledge. Thus, in Study 1, we examined adults' (n = 25) memory integration of new facts with prior knowledge. The participants had 52% accuracy in self-derivation. In Study 2 (n = 86), we examined whether reactivating prior knowledge before the novel fact presentation facilitated self-derivation through integration with prior knowledge. Results indicated that performance was significantly higher for those whose prior knowledge was directly reactivated (55% accuracy) in comparison with the control group (42%). Pedagogical implications are discussed.