How much morphological variation can children tolerate when identifying familiar words? This is an important question in the context of the acquisition of richly inflected languages where identical word forms occur far less frequently than in English. To address this question, we compared children’s (N = 96, mean age 4;1, range 2;11–5;1) and adults’ (N = 96, mean age 21 years) tolerance of word-onset modifications (e.g., for stug: wug and wastug) and pseudoaffixes (e.g., kostug and stugko) in a labelextension task. Word-form modifications were repeated within each experiment to establish productive inflectional patterns. In two experiments, children and adults exhibited similar strategies: they were more tolerant of prefixes (wastug) than substitutions of initial consonants (wug), and more tolerant of suffixes (stugko) than prefixes (kostug). The findings point to word-learning strategies as being flexible and adaptive to morphological patterns in languages.