Knowledge updating occurs when people learn about the impacts of variables on memory after experiencing their effects. For instance, judgments of learning (JOLs) for encoding strategies (e.g., imagery and repetition) show no difference during a first study–test trial; however, during a second trial, JOLs better reflect the benefits of the more effective strategy. Although this outcome indicates some knowledge updating, JOLs on a second trial rarely update to reflect the full impact of a given variable. We investigated several explanations for this incomplete updating. Evidence using prestudy JOLs from Experiments 1 and 2 disconfirmed the encoding-disrupts-updating (EDU) hypothesis, which is that the experience of encoding items on the second trial disrupts the use of new knowledge in making JOLs. In Experiment 3, we used binary JOLs to evaluate whether the lack of updating is an artifact of people not wanting to use extreme ratings, which accounted for some—but not all—of the incomplete updating. Finally, in Experiment 4, immediately after the test on the initial trial, participants received feedback about how many items they had recalled for each level of the focal variable, and their JOLs on the second trial still showed incomplete updating. Taken together, the evidence suggests that incomplete knowledge updating on JOLs arises from multiple factors, including a scaling artifact and the deficient use of accurate knowledge when making JOLs.