Pasteur's Birthday Cake

I really like this movie, so the following is not meant as a criticism:

I know this movie was not made in France, but were the people who made this film so afraid/stupid that they wrote "Happy Birthday" in his cake, so we would know what's going on? I mean, this did take place in France. "Bon Anniversaire" would have been correct. Maybe they felt there were too many letters to fit on the cake?