The purpose of this study is to expand the testing ground of the Interface Hypothesis (Sorace, 2006) by investigating the degree to which second language (L2) learners of Bulgarian with English as their first language (L1) had acquired the pragmatic function of clitic doubling as a topicality marker. Advanced and intermediate L2 speakers of Bulgarian, as well as a control group of Bulgarian native speakers, participated in the experiment. The experimental materials included a proficiency test and a pragmatic felicity task. The results showed that the intermediate participants did not differentiate between the felicitous and the infelicitous options in the pragmatic felicity task in a target-like manner as their responses either did not exhibit a statistically significant difference or favored the response closest to the L1. However, the advanced L2 learners had successfully acquired the pragmatic meaning of clitic doubling in Bulgarian and performed in a native-like manner. The study highlights the fact that successful learning at the syntax-discourse interface cannot be excluded, and more research--exploring as many interface conditions as possible--needs to be carried out in order to validate the Interface Hypothesis as a legitimate constraint that permanently hinders native-like performance. (Contains 3 tables, 4 figures and 9 notes.)