Dyslexic children often fail to correct errors while reading aloud, and dyslexic adolescents and adults exhibit lower amplitudes of the error-related negativity (ERN)--the neural response to errors--than typical readers during silent reading. Past researchers therefore suggested that dyslexia may arise from a faulty error detection mechanism that interferes with orthographic learning and text comprehension. An alternative possibility is that comprehension difficulty in dyslexics is primarily a downstream effect of low-quality lexical representations--that is, poor word knowledge. On this view, the attenuated ERN in dyslexics is a byproduct, rather than a source, of underdeveloped orthographic knowledge. Because the second view implies a direct association of the error response with comprehension skill in populations of all ability levels, the present study evaluates these alternatives through a reanalysis of behavioral and neural data from 31 typical adult readers. If it is true that faulty error processing can manifest as dyslexia, a model in which error monitoring contributes directly to comprehension should outperform a model in which it does not. ERNs recorded during spelling judgments were used as a measure of error detection aptitude in path analyses of reading comprehension. The data were better fit by a model in which error detection aptitude was a consequence of word knowledge than a model in which it contributed directly to comprehension. The findings challenge the notion that comprehension difficulty in dyslexics is attributable to error processing deficits and are consistent with the hypothesis that comprehension difficulty in dyslexics is partially attributable to low-quality word knowledge.