why this regexp returns match?

http://ift.tt/1zbhuZf

var reg = /^(?!managed).+\.coffee$/
var match = '20150212214712-test-managed.coffee'.match(reg)
console.log(match) // prints '20150212214712-test-managed.coffee'

I want to match regexp only if there is not word "managed" present in a string - how I can do that?