I have issue with wallpaper. When I am switching desktop, wallpaper is not moving along but "stays under". killall Dock fixes this but recently it is occurring so often that it became annoying.

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What could be issue? Is there permanent solution?

2 Answers 2


It's not obvious to me why the killall Dock command would help with this, but since it does it may be worth you doing a reset and restart of the Dock.

Reset and restart the Dock

If you go ahead with resetting and restarting the Dock you will need to re-add any non-default icons to your Dock. (I usually find it's a good opportunity for people to start afresh and only add things as they actually use them).

To reset and restart the Dock follow these steps:

  • Go to Finder
  • Press and hold the option key down
  • Now go to the Go menu
  • Select the Library option to open the User's Library folder. You can let go of the option key now.
  • Go to the Preferences folder (i.e. within the Library folder)
  • Find and move the com.apple.dock.plist file to the Trash
  • Now open Terminal (usually located in Applications > Utilities)
  • Enter this command killall -KILL Dock
  • Press enter

Remember you'll need to re-add some apps back to the Dock.

If this doesn't resolve your issue, it'd be worth also testing what happens when you're booted into Safe Mode and afterwards again. See below.

Boot into Safe Mode

Follow these steps to boot your Mac into Safe Mode:

  1. Fully shut down your Mac
  2. Restart your Mac
  3. Immediately press the Shift key and keep it down
  4. Let go of the Shift key when you see the login window (NOTE: If you have FileVault enabled you may need to log in twice).
  5. Take a note of what happens (i.e. switch desktops and take note of what happens with your Desktop Background)
  6. Exit Safe Mode by restarting your Mac as normal
  7. Switch desktops again and take note of what happens with your Desktop Background

Once you've booted into Safe Mode, let me know how you went.

  • Thank you! I will try first reset and restart of Dock. If it will not help I will check this issue in Safe Mode.
    – Spodym
    Apr 20, 2017 at 12:40

It took me some time to resolve it but I noticed relation between my issue and this BUG appearing in system.log:

Jun 20 09:32:48 myhost Dock[81166]: BUG in libdispatch client: kevent[EVFILT_MACHPORT] monitored resource vanished before the source cancel handler was invoked

Moreover I noticed connection between bug occurrences and my tasks performed. Bug was appearing only when I was using Sublime Text 3. I changed it for another code editor and since then I did not have this issue.

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