diff --git a/wcs_olap/cmd.py b/wcs_olap/cmd.py
index 1fb0624..b1ca346 100644
--- a/wcs_olap/cmd.py
+++ b/wcs_olap/cmd.py
@@ -41,7 +41,7 @@ def main2():
     locale.setlocale(locale.LC_ALL, '')
     parser = argparse.ArgumentParser(description='Export W.C.S. data as a star schema in a '
                                      'postgresql DB', add_help=False)
-    parser.add_argument('config_path', default=None)
+    parser.add_argument('config_path', nargs='?', default=None)
     group = parser.add_mutually_exclusive_group()
     group.add_argument("-a", "--all", help="synchronize all wcs", action='store_true',
                        default=False)