diff --git a/nova/flags.py b/nova/flags.py
index bc4fd475..1f85b309 100644
--- a/nova/flags.py
+++ b/nova/flags.py
@@ -71,8 +71,20 @@ class FlagValues(object):
         self._parser = optparse.OptionParser()
         self._parser.disable_interspersed_args()
         self._extra_context = extra_context
+        self._multistring_defaults = {}
         self.Reset()
 
+    def _apply_multistring_defaults(self, values):
+        #
+        # This horrendous hack is to stop optparse appending
+        # values to the default value. See:
+        #   http://bugs.python.org/issue5088
+        #
+        for flag, default in self._multistring_defaults.items():
+            if not getattr(values, flag):
+                setattr(values, flag, default)
+        return values
+
     def _parse(self):
         if not self._values is None:
             return
@@ -101,6 +113,8 @@ class FlagValues(object):
         finally:
             self._parser.error = error_catcher.orig_error
 
+        values = self._apply_multistring_defaults(values)
+
         (self._values, self._extra) = (values, extra)
 
     def __call__(self, argv):
@@ -190,7 +204,8 @@ class FlagValues(object):
                          action='callback', callback=parse_list)
 
     def define_multistring(self, name, default, help):
-        self._add_option(name, default, help, action='append')
+        self._add_option(name, [], help, action='append')
+        self._multistring_defaults[name] = default
 
 FLAGS = FlagValues()
 
diff --git a/nova/tests/test_flags.py b/nova/tests/test_flags.py
index dab11c5e..2865eef5 100644
--- a/nova/tests/test_flags.py
+++ b/nova/tests/test_flags.py
@@ -74,7 +74,11 @@ class FlagsTestCase(test.TestCase):
         self.assertEqual(self.FLAGS.float, 6.66)
 
     def test_define_multistring(self):
-        flags.DEFINE_multistring('multi', [], 'desc', flag_values=self.FLAGS)
+        flags.DEFINE_multistring('multi', ['blaa'], 'desc',
+                                 flag_values=self.FLAGS)
+
+        self.assert_(self.FLAGS['multi'])
+        self.assertEqual(self.FLAGS.multi, ['blaa'])
 
         argv = ['flags_test', '--multi', 'foo', '--multi', 'bar']
         self.FLAGS(argv)