Yes, absolutely normal. Grizzly does the same thing and it didn't take him long to learn what the words, "Time out" mean! I put him in the corner with a baby gate (makes a triangle-from wall to wall - putting him in the corner) I only make him stay for 2-3 minutes but as far as he is concerned - that's long enough! I won't stand for him nipping at us or growling unless it's his playing growl. And there is a difference.
Last night he wound up in time out twice.
Last night he wound up in time out twice.