diff --git a/.DS_Store b/.DS_Store
new file mode 100644
index 0000000..a5c2315
Binary files /dev/null and b/.DS_Store differ
diff --git a/pecan/commands/base.py b/pecan/commands/base.py
index 5451444..c167c49 100644
--- a/pecan/commands/base.py
+++ b/pecan/commands/base.py
@@ -78,7 +78,10 @@ class CommandRunner(object):
             )
             for arg in getattr(cmd, 'arguments', tuple()):
                 arg = arg.copy()
-                sub.add_argument(arg.pop('command'), **arg)
+                if isinstance(arg.get('command'), basestring):
+                    sub.add_argument(arg.pop('command'), **arg)
+                elif isinstance(arg.get('command'), list):
+                    sub.add_argument(*arg.pop('command'), **arg)
 
     def run(self, args):
         ns = self.parser.parse_args(args)
diff --git a/pecan/commands/shell.py b/pecan/commands/shell.py
index dee6aa5..3424103 100644
--- a/pecan/commands/shell.py
+++ b/pecan/commands/shell.py
@@ -10,7 +10,7 @@ import sys
 class NativePythonShell(object):
 
     @classmethod
-    def invoke(cls, ns, banner):
+    def invoke(cls, ns, banner):  # pragma: nocover
         import code
         py_prefix = sys.platform.startswith('java') and 'J' or 'P'
         shell_banner = 'Pecan Interactive Shell\n%sython %s\n\n' % \
@@ -26,7 +26,7 @@ class NativePythonShell(object):
 class IPythonShell(object):
 
     @classmethod
-    def invoke(cls, ns, banner):
+    def invoke(cls, ns, banner):  # pragma: nocover
         try:
             from IPython.frontend.terminal.embed import (
                 InteractiveShellEmbed
@@ -51,7 +51,7 @@ class ShellCommand(BaseCommand):
     }    
 
     arguments = BaseCommand.arguments + ({
-        'command': '--shell',
+        'command': ['--shell', '-s'],
         'help': 'which Python shell to use',
         'choices': SHELLS.keys(),
         'default': 'python'