I am opening an old project created in 2019.3 inside my new Unity 2019.4. I got this error message in Unity Console:

Library/PackageCache/com.unity.xr.arsubsystems@2.2.0-preview.3/Runtime/ImageTrackingSubsystem/XRImageTrackingSubsystem.cs(57,30): error CS0506: 'XRImageTrackingSubsystem.Destroy()': cannot override inherited member 'Subsystem.Destroy()' because it is not marked virtual, abstract, or override

Please note that this current project does not use anything related to AR "Augmented Reality" or XR package.

I have already Googled this error message, but have not seen a solution yet.

However, I guess that this error likely comes from some conflicts in the AR or XR versions.

To fix this error, should I install or update the basic Unity XR or AR package ?

Thank you very much.

  • \$\begingroup\$ "To fix this error, should I install or update the basic Unity XR or AR package ?" That sounds like a reasonable troubleshooting step you can try without waiting on Internet strangers to give you the green light. What happens when you try it? \$\endgroup\$
    – DMGregory
    Apr 4, 2021 at 11:46
  • 1
    \$\begingroup\$ When I looked into this problem, I came across this SO post - have you tried changing the package version as described in the solutions there? \$\endgroup\$
    – Pikalek
    Apr 4, 2021 at 21:40
  • \$\begingroup\$ I have figured out and posted the answer to my own question in this page. Thanks to all for your suggestions. \$\endgroup\$ Apr 4, 2021 at 22:13

1 Answer 1


I've figured out the answer to my own question. Here are the steps that help me to solve the issue:

  1. Open Package Manager (From "Window" -> "Package Manager")
  2. Upgrade or install the latest version of the following packages:

AR Foundation

AR Subsystems

ARKit Face Tracking

ARKit XRPlugin

XR Plugin Managerment

XR Legacy Input helpers

XR Interaction Subsystems


  1. You may not need to install/upgrade all of those packages unless the errors do not go away. Sometimes, you just need to upgrade/install 1 or 2 packages to solve the issues.
  2. Usually, you have to upgrade to the latest versions of the packages to fix the issue. But, some times, you need to go back to the previous or older versions of the packages because the latest versions may have a bug.
  3. There may be more AR or XR packages you need to install/upgrade as the list may grow when Unity adds more features in the future.

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