Index: Lib/test/test_argparse.py
===================================================================
--- Lib/test/test_argparse.py	(revision 83528)
+++ Lib/test/test_argparse.py	(working copy)
@@ -3782,6 +3782,20 @@
             # 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 in (1, 2, 3, '?', '*', '+'):
+                should_fail = ((isinstance(nargs, int) and len(metavars) > nargs)
+                               or (nargs == '?' and len(metavars) != 1))
+                if should_fail:
+                    self.assertValueError('--foo', nargs=nargs, metavar=metavars)
+                else:
+                    # There's no self.assertNoValueError; I assume that letting the error
+                    # itself propagate is good enough to show an unwanted exception here
+                    parser = argparse.ArgumentParser()
+                    parser.add_argument('--foo', nargs=nargs, metavar=metavars)
+
     def test_more_than_one_argument_actions(self):
         for action in ['store', 'append']: