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Fixed in 5.6.0



Found in


Issue ID




UnityEngine.UI.dll is in timestamps but is not known in guidmapper...

Error message shown on first open of attached project:

Asset 'C:/Program Files (x86)/Unity/Editor/Data/UnityExtensions/Unity/GUISystem/4.6.0/UnityEngine.UI.dll' is in timestamps but is not known in guidmapper...

Comments (85)

  1. jinhaifeng

    Oct 12, 2016 17:08

    This is embarrassing unity... I've had to completely remove my project and re-clone it from git to get rid of these issues.

  2. mbrindic

    Oct 05, 2016 15:36

    It happens after I import Google Play Games Services plugin. My platform is iOS. I cannot continue my development because each time I press Play, Unity crashes...

  3. Sky286

    Oct 04, 2016 07:35

    We are still experiencing this in Unity 5.4.1f1, causes serious workflow issues. Please fix : )

  4. pixelmagetoby

    Sep 28, 2016 22:09

    Everyone on the team gets this from time to time, our entire project gets screwed up, then we wind up needing to delete library and relaunch (currently takes over an hour to complete since our project is so big). Multiplied by the size of the team this is costing serious $$$$.

  5. Free286

    Sep 28, 2016 07:42

    Get this every day, has been like this for years now.

  6. synapsemassage

    Sep 27, 2016 14:26

    Unluckily, I'm on the same boat like you guys. I'm still onUnity 5.0.1f1 and as I can see it doesn't make sense to update. That's really bad.

  7. vdescubes

    Sep 22, 2016 00:25

    I have to close Unity, move the content from Data\UnityExtensions extensions folder to a temp place, open Unity, close Unity, move the content back back, open Unity.
    The work around lasts until it breaks again...

  8. alexd_eps

    Sep 01, 2016 09:21


    Happens for us regularly when doing asset bundle builds via BuildPipeline.BuildAssetBundles (ie, Unity5 asset bundle build).

    Means we are stuck using our old U4 build system until the issue is fixed - we can't afford the reimport times as our projects are very large.

  9. wightwhale

    Aug 25, 2016 17:46

    Still in 5.4.0f2

  10. BisuDagger

    Aug 25, 2016 14:51

    This issue occurs too frequently and costs my employees 2 hrs reimport time because the project is so large. Please give this some attention.

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