   insertAt: (index, value) ->
     mark(@, value)
     Array.prototype.splice.call(@, index, 0, value)
+    @length = getLength(@)
     @trigger("insert", index, value)
     @trigger("change", @)
     value

  push: (element) ->
    @[@length] = element
    mark(@, element)
    @trigger("add", element)
    @trigger("change", @)
    element

    value = @[index]
    unmark(@, value)
    Array.prototype.splice.call(@, index, 1)
    @length = getLength(@)
    @trigger("delete", index, value)
    @trigger("change", @)
    value
