The present study addresses a learnability problem in the acquisition of English progressive aspect by Korean learners of English. As Korean and English differ in the way that the lexical aspect of verbs interacts with progressive morphology, we predicted that Korean learners of English would be affected by their L1 aspectual system, accepting non-targetlike combinations of lexical aspect and aspectual morphology. Sixty Korean university students were presented with sentences containing different aspectual classes of verbs in two conditions—the progressive and the simple present—and were asked to judge the naturalness of the sentences. The results showed that the majority of the learners erroneously accepted progressive sentences containing stative verbs. It also showed that the learners accepted simple present constructions containing eventitive verbs for an ongoing interpretation,indicating the pervasiveness of L1 transfer. The findings strongly suggest that Korean EFL learners have difficulty ruling out erroneous form-meaning associations based on their L1 progressive morphology.