The present study investigated Korean learners' knowledge on the range of possible interpretations of English locative PPs with manner of motion verbs, and considers whether learners can arrive at a superset L2 grammar on the basis of positive L2 input. Unlike Korean, some English locative PPs occurring with manner of motion verbs (such as in John jumped on the bed) are ambiguous as they can be interpreted as either directional or locational. Thirty Korean learners of English in three distinct groups (Advanced EFL-only group; Intermediate-EFL-only group; and ESL-experienced group) participated in an experimental study, along with a control group of nine native speakers of English. The results of the study showed that I) Korean learners, overall, tended to interpret English locative PPs as only locational, failing to recognize the ambiguity between the directional and locational readings in the target structure; 2) For the learners who experienced only the EFL context, even highly proficient learners, as well as intermediate level learners, failed to acknowledge the ambiguity; 3) The learners who experienced the ESL context for an extended period of time could identify the target reading to some extent, although they still could not reach the native-like competence. From these results, it is argued that robustness of positive evidence, not simply its availability, is critical in the acquisition of the superset L2 targets like the present one.