diff -r e129fcc720c1 -r 48c0c3bc40dd Admin/mira.py
--- a/Admin/mira.py	Wed Dec 19 16:41:55 2012 +0100
+++ b/Admin/mira.py	Thu Dec 20 09:49:00 2012 +0100
@@ -122,7 +122,7 @@
     prepare_isabelle_repository(isabelle_home, None, more_settings=more_settings)
     os.chdir(isabelle_home)
 
-    args = (['-o', 'timeout=%s' % timeout] if timeout is not None else []) + cmdargs
+    args = (['-o', 'timeout=%s' % timeout] if timeout is not None else []) + list(cmdargs)
 
     # invoke build tool
     (return_code, log) = env.run_process('%s/bin/isabelle' % isabelle_home, 'build', '-s', '-v', *args)