diff -r 54fb77e0762c Lib/test/test_argparse.py
--- a/Lib/test/test_argparse.py	Thu Jun 23 14:22:59 2011 +0200
+++ b/Lib/test/test_argparse.py	Fri Jun 24 08:25:37 2011 +0200
@@ -1189,6 +1189,7 @@
 
 class TestEmptyAndSpaceContainingArguments(ParserTestCase):
 
+    parser_signature = Sig(fromfile_prefix_chars='@')
     argument_signatures = [
         Sig('x', nargs='?'),
         Sig('-y', '--yyy', dest='y'),