Commentary for Avodah Zarah 145:5

The mishnah seems to say that even the smallest amount of yayin nesekh renders the wine it falls into prohibited. This is a clear contradiction to R. Dimi.
The Talmud answers that the mishnah refers only to when permitted wine falls into prohibited wine. But if prohibited wine falls into permitted wine, it is nullified. [This is clearly not the simple reading of the mishnah].