Index: Lib/test/test_argparse.py
===================================================================
--- Lib/test/test_argparse.py	(revision 83730)
+++ Lib/test/test_argparse.py	(working copy)
@@ -3847,6 +3847,24 @@
             # nargs is always disallowed
             self.assertTypeError('-x', nargs='*', action=action)
 
+    def test_wrong_number_of_metavars(self):
+        "Verify that a tuple of metavars that disagrees with nargs raises error immediately."
+        for metavars in ('X', ('X', ), ('X', 'Y'), ('X' ,'Y', 'Z')):
+            for (nargs, nmetavars) in ( (1, (1,)),
+                                        (2, (1, 2)),
+                                        (3, (1, 3)),
+                                        ('?', (1,)),
+                                        ('*', (2,)),
+                                        ('+', (2,)),
+                                        ):
+                if len(metavars) in nmetavars:
+                    # There's no self.assertNoValueError; I assume that letting the error
+                    # itself propagate is good enough to show any unwanted exception here
+                    parser = argparse.ArgumentParser()
+                    parser.add_argument('--foo', nargs=nargs, metavar=metavars)
+                else:
+                    self.assertValueError('--foo', nargs=nargs, metavar=metavars)
+
     def test_more_than_one_argument_actions(self):
         for action in ['store', 'append']: