What do I do about my 5 year-old son and husband "ing" heads?

My five year old son is very well behaved in school and his extra-curricular activities. I stay at home with my children and throughout the day with me he is polite and sweet though he has momentary lapses of siness that I believe to be normal. I do NOT believe in so I use time-outs and those seem to work. However, when my husband comes home, my son starts to misbehave. He gets loud and crazy and my husband makes empty threats and doesn't follow through. This is starting to cause problems between my husband and I as he thinks that I am not disciplining my son enough. I don't know what to do. I'm starting to think that it is a lack of maturity on my husband's part more than anything. Does anyone have any constructive thoughts on how to handle this?