diff --git a/tensorboard/program.py b/tensorboard/program.py
index e6048bcc47..938f17ab20 100644
--- a/tensorboard/program.py
+++ b/tensorboard/program.py
@@ -177,7 +177,6 @@ def configure(self, argv=('',), **kwargs):
         description=('TensorBoard is a suite of web applications for '
                      'inspecting and understanding your TensorFlow runs '
                      'and graphs. https://github.com/tensorflow/tensorboard '))
-    base_parser.set_defaults(**{_SUBCOMMAND_FLAG: _SERVE_SUBCOMMAND_NAME})
     subparsers = base_parser.add_subparsers(
         help="TensorBoard subcommand (defaults to %r)" % _SERVE_SUBCOMMAND_NAME)
 
@@ -208,6 +207,11 @@ def configure(self, argv=('',), **kwargs):
 
     with argparse_util.allow_missing_subcommand():
       flags = base_parser.parse_args(argv[1:])  # Strip binary name from argv.
+    if getattr(flags, _SUBCOMMAND_FLAG, None) is None:
+      # Manually assign default value rather than using `set_defaults`
+      # on the base parser to work around Python bug #9351 on old
+      # versions of `argparse`: <https://bugs.python.org/issue9351>
+      setattr(flags, _SUBCOMMAND_FLAG, _SERVE_SUBCOMMAND_NAME)
 
     self.cache_key = manager.cache_key(
         working_directory=os.getcwd(),