diff --git a/commandr/commandr.py b/commandr/commandr.py
index bd84ff2..3fe95a5 100644
--- a/commandr/commandr.py
+++ b/commandr/commandr.py
@@ -389,6 +389,9 @@ def _BuildOptParse(self, argspec, defaults_dict):
         elif repr(defaults_dict[arg]) == 'True':
           self._AddOption(args, dest=arg, action='store_false',
                       default=True)
+        elif isinstance(defaults_dict[arg], list):
+          self._AddOption(args, dest=arg, action='append', 
+                      type='string', default=defaults_dict[arg])
         else:
           if isinstance(defaults_dict[arg], int):
             arg_type = 'int'