Talking in sleep

My bf talks in his sleep and we've been together for a year so I'm used to it. But sometimes we found out he speaks french in his sleep. He has never taken french speaking classes and doesn't even like french people. But tonight it was something different than usual... usually it's just a single word. But tonight it was a hole sentence. "Je t'aime de tout mon coeur" (I think it translated right but it's supposed to be I love you with all my heart) he has never said I love you. Within our year of being together. It's probably nothing but it made me happy.