cannot unzip exported anyfile.csv.zip with 4.12 beta

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Status: open

Owner: nobody

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Priority: 5

Updated: 2012-12-07

Created: 2004-12-03

Creator: Anonymous

Private: No

I cannot unzip any .csv.zip file exported as zipped csv
data with phpmyadmin
7zip returns the error message :
file.csv.zip is not supported archive