How to solve error 'Invalid mex file'

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Abi Wyllie
Abi Wyllie on 11 Apr 2022
Answered: Ganesh Gudipati on 14 Apr 2022
I am trying to run a script on MATLAB using the psychtoolbox, but I keep getting this error -
'Invalid MEX-file ‘C:\toolbox\Psychtoolbox\PsychBasic\MatlabWindowsFilesR2007a\Eyelink.mexw64’: The specified module could not be found.'
The mex file is right there when I go into the MatlabWindowsFiles folder, and I have installed the GStreamer runtime and vcredist. I have also tried the Dependency Walker to find missing .dll files, and everything is added to my path, but I still get the error.
I am working on a Windows 10 laptop with a 64-bit operating system and a x64-based processor. The MATLAB versions I have is R2020b.
I cannot think of anything else to try so any suggestions would be greatly appreciated.
Thank you!
Abi Wyllie
Abi Wyllie on 11 Apr 2022
I think so - I downloaded the vcredist_x64_2015-2019 as specified in the Psychtoolbox page ( - step 4) and I have tried to download the dependency walker again and it gave me no new .dll files like last time and when I opened the dependency walker window I couldn't find anything written there.

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Answers (1)

Ganesh Gudipati
Ganesh Gudipati on 14 Apr 2022
Generally the first step is to check if the mupadmex.mexw64 file is present in path shown in the error. And, you already did it.
Now make sure, you have permissions to read and execute this file.
If you have the file and permissions but still you are facing an issue, then the problem may be realted to a false detection from an antivirus program. Please check your antivirus software to see if there have been any files quarantined from your MATLAB installation. If there are files from your MATLAB installation directory that have been quarantined, please restore them.
Then, you may need to create an exception in your antivirus program for the MATLAB installation folder and it's subfolders.
Check this Previous MATLAB answer if required.
Hope this helps.




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