diff --git a/Lib/distutils/cmd.py b/Lib/distutils/cmd.py
--- a/Lib/distutils/cmd.py
+++ b/Lib/distutils/cmd.py
@@ -4,7 +4,7 @@
 in the distutils.command package.
 """
 
-import sys, os, re
+import sys, os, re, types
 from distutils.errors import DistutilsOptionError
 from distutils import util, dir_util, file_util, archive_util, dep_util
 from distutils import log
@@ -209,7 +209,7 @@
         if val is None:
             setattr(self, option, default)
             return default
-        elif not isinstance(val, str):
+        elif not isinstance(val, types.StringTypes):
             raise DistutilsOptionError("'%s' must be a %s (got `%s`)"
                                        % (option, what, val))
         return val