Selling a Slave outside the Land of Israel

The sages taught (t. Avodah Zarah 3:18): [With regard to] one who sells his slave to [a Jew] outside of Erets [Yisrael, the slave] is emancipated, but [he nevertheless] requires a bill of manumission from his second master. Rabban Simeon ben Gamaliel says: Sometimes he is emancipated and sometimes he is not emancipated. How so? [If the master] said: So-and-so my slave, I sold him to so-and-so of Antioch, [then] he is not emancipated, [because it is possible that he describes the purchaser this way because he was born in Antioch, and now he lives in Erets Yisrael. However, if he said: I sold him] to [so-and-so] of Antioch who is in Antioch, [then] he is emancipated, [as his statement clarifies that he is selling his slave to one who lives outside of Erets Yisrael].