Nonce-probe test has been extensively used to investigate the productivity of tone sandhi. The nonce words used in previous studies on Xiamen tone sandhi were usually disyllabic wug words with accidental-gap syllables. This study aims at isolating the effect of phonotactic constraints by investigating the application of Xiamen tone sandhi to both (1) disyllabic semi-wug words made up of real syllables and (2) disyllabic wug words consisting of one accidental-gap syllable and one real syllable. Picture-naming tasks were used to elicit the production of these conditions from children, teenagers, middle-aged adults and older speakers. The results showed that Xiamen tone sandhi was highly productive for semi-wug words but far less productive for wug words. Children and teenagers made some errors in applying the correct tone sandhi rules to real and semi-wug words, while their accuracy of applying tone sandhi to wug words was very similar to those of the middle-aged and older speakers. It is concluded that Xiamen tone sandhi is highly productive in phonotactically well-formed real syllables but less productive in phonotactically ill-formed syllables.