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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. karl_jones

    Sep 21, 2015 21:32

    If you still have issues please file a bug report, comments here may be missed -

  2. Wolfram

    Sep 18, 2015 16:27

    TYRANNICUS100BC's comment (2015/05/26) is the "hardcore" solution. however, just adding this script and running it from the Menu works nicely:

  3. zero_null

    Sep 18, 2015 07:45

    This Issue is Still Present on Unity 5.2.0f3
    I am on Windows and Using Unity Personal

  4. CipSoft

    Sep 18, 2015 07:05

    Just happened to me again in 5.2.0f3. Does not look like it is fixed.

    My Unity installation Path is
    C:\Program Files\Unity.5.1.2\

  5. franbat

    Jul 18, 2015 18:39

    I had this problem but the answer written by MARKOXENHAMJUN in 03, 2015 07:30 has saved me. Thanks guy!!

  6. HonoraryBob

    Jul 13, 2015 21:09

    This problem hit me suddenly today across several projects - but oddly with different errors in different projects - along with random other problems (unrelated scripts missing all over the place, at least one of my own scripts actually deleted (the file itself is no longer on the hard drive) at random, keyboard control no longer working in one project but fine in the others even though they use the same code, etc).

  7. tayl0r

    Jul 08, 2015 00:38

    That workaround never works for me, on Windows. I am stuck reimporting Assets every time this happens to me, which is almost daily now. Very painful bug.

  8. k0mbain

    Jun 25, 2015 13:58

    It seems like all UnityExtensions are causing this problem, because I had to extend below solution with removing/restoring all three folders from Unity/Editor/Data/UnityExtensions:

    Rene, can you provide any news about fixing it?

  9. Desktopdaydreams

    Jun 19, 2015 08:44

    Hey Folks,

    We got the error again this morning after renaming a folder. Working in 5.0.3f2.

    As usual the fix from TYRANNICUS100BCMAY is working (thank you).

    "Best work around we've found:
    1. Quit Unity
    2. Move UnityEngine.UI.dll and UnityEditor.UI.dll to your desktop
    3. Relaunch Unity
    4. Quit Unity
    5. Move UnityEngine.UI.dll and UnityEditor.UI.dll back to their original location
    6. Relaunch Unity"


  10. aresundnes

    Jun 17, 2015 11:21

    Still happening in 5.1. Also now, the same thing is happening with the networking dll.

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