Toddler biting dog---?

My 20 month old over the past week has bit our dog at least three times that I am aware of. Twice he has chomped her tail and once on the scruff of her neck. He doesn't bite people. He seems to understand that he shouldn't do it, given the smile he gives me as he goes in for the chomp. The dog is very sweet, has not shown any aggression towards anyone, etc, but she is clearly not too keen about it. I have been redirecting by boy anytime his head is near the dog. The bites have been consequenced with a stern "No" and a time out. Anyone else with any experience? Hopefully this phase will be as short as his phase of trying to drink out of the dogs water dish was.