Early on after their tentative truce, Joe and Nicky are traveling together. Joe assumes Nicky is ignoring him because he doesn't speak Arabic or was just being rude because he still views Joe as an enemy... either way, he has yet to hear Nicky respond to anything he's said so far. Little did he know, Nicky is actually mute.

+ Nicky makes no attempt to explain that's he can't speak which doesn't help with the misunderstanding. He just thought Joe already knew.
++ Joe and Nicky make their own sign language to communicate.