diff --git a/Lib/argparse.py b/Lib/argparse.py
index e45b67b..a300828 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -593,7 +593,10 @@
         elif action.nargs == SUPPRESS:
             result = ''
         else:
-            formats = ['%s' for _ in range(action.nargs)]
+            try:
+                formats = ['%s' for _ in range(action.nargs)]
+            except TypeError:
+                raise ValueError("invalid nargs value") from None
             result = ' '.join(formats) % get_metavar(action.nargs)
         return result
 
@@ -850,7 +853,7 @@
                  help=None,
                  metavar=None):
         if nargs == 0:
-            raise ValueError('nargs for store actions must be > 0; if you '
+            raise ValueError('nargs for store actions must be != 0; if you '
                              'have nothing to store, actions such as store '
                              'true or store const may be more appropriate')
         if const is not None and nargs != OPTIONAL:
@@ -942,7 +945,7 @@
                  help=None,
                  metavar=None):
         if nargs == 0:
-            raise ValueError('nargs for append actions must be > 0; if arg '
+            raise ValueError('nargs for append actions must be != 0; if arg '
                              'strings are not supplying the value to append, '
                              'the append const action may be more appropriate')
         if const is not None and nargs != OPTIONAL: