A quick question for Christians?

Heaven is considered a utopia amongst almost all christians. In order for a Utopia to exist everything is required to be perfect. Humans however are flawed in many ways, and any human being sent to heaven would make heaven imperfect. The only way for heaven to remain a Utopia would be to essentially change the personality of all of its citizens to one that would be considered perfect and doing that in itself is unjust making heaven imperfect as well. How can heaven be considered a Utopia with humans roaming inside.