Now there with us was a Hebrew youth—a slave belonging to the commander of the bodyguards. When we told him, he interpreted our dreams for us, each man’s dream he interpreted.
Genesis 41:12 TLV

Why did the cupbearer say that Joseph was a "young Hebrew slave"? Why was that important? It could have been CYA in case it didn't work out for Pharaoh: "It worked for me, but he's just a young Hebrew slave, so don't expect too much."