'start' props (player-vars) does not work

[sbyeol3]

code is

<youtube :video-id="lecture.video_id"
     @ready="ready"
     @paused="saveCurrentTime"
     @ended="saveCurrentTime"
      :player-vars="{start: 100, autoplay: 1}">
</youtube>

'props' in Vue DevTools is

mute:false
playerHeight:"390"
playerVars:Object
autoplay:1
start:100
playerWidth:"640"
videoId:"QODxI9iTj9M"

'autoplay' prop does work. but 'start' does not work. The video starts at 0:00 Module version is 2.2.1.

Please Help me..