In this study we examined how two students viewed the general nature of their proportional reasoning errors as they attempted to generalize numeric situations. Using a teaching experiment methodology we studied the reasoning of two students over 18 instructional sessions. One student, Dallas, appeared to recognize that the proportional reasoning error applied to all cases of a particular problem situation and began to apply this reasoning across problems. The other student, Lloyd, exhibited difficulty seeing the generality of his mistaken use of proportional reasoning and regularly repeated this error during the study. From the data we developed a schematized description of how students view the generality of their errors and tracked the changes in these views over the course of the study. We analyze how Dallas and Lloyd's perception of errors shaped their understanding of proportional reasoning and provide suggestions for the role errors play in restructuring a student's conceptual schema.