     @tailed
 
   isValid: ->
-    true
+    @valid
 
   getInvalidationStrategy: ->
     @invalidate


    if tailed? and tailed isnt @tailed
      @tailed = tailed
      updated = true

    if state? and not isEqual(state, @state)

    oldState = @getState()

    updated = false
    {range, reversed, tailed, valid, state} = patch.newParams

    if range? and not range.isEqual(@range)
      @range = range.freeze()
