Index: /trunk/src/VBox/ValidationKit/testdriver/testfileset.py
===================================================================
--- /trunk/src/VBox/ValidationKit/testdriver/testfileset.py	(revision 83622)
+++ /trunk/src/VBox/ValidationKit/testdriver/testfileset.py	(revision 83623)
@@ -514,5 +514,8 @@
         # Open the tarball:
         try:
-            oTarFile = tarfile.open(sTarFileHst, 'w:gz');
+            # Make sure to explicitly set GNU_FORMAT here, as with Python 3.8 the default format (tarfile.DEFAULT_FORMAT)
+            # has been changed to tarfile.PAX_FORMAT, which our extraction code (vts_tar) currently can't handle.
+            ## @todo Remove tarfile.GNU_FORMAT and use tarfile.PAX_FORMAT as soon as we have PAX support.
+            oTarFile = tarfile.open(sTarFileHst, 'w:gz', format = tarfile.GNU_FORMAT);
         except:
             return reporter.errorXcpt('Failed to open new tar file: %s' % (sTarFileHst,));