     #@check_stage key
     if @stage == @last_stage
       @notify_dep key
-    if @sticky[key]
+    if @sticky[key]?
       @sticky[key]
     else if @cycle[key] && on_cycle
       @cache[key] ?= on_cycle()

  _.extend (Worker.mixins ?= {}), mixins
  _.extend Worker.prototype, mixins

module.exports = Worker
  check_values: (arr) ->
    bad = []
    for dep, i in @deps
      try
        @cache[dep] = JSON.parse arr[i]
      catch e
        throw new Error "Cannot parse JSON for #{dep}: #{arr[i]}"
      bad.push dep unless @cache[dep]?
    bad

