diff --git a/Lib/argparse.py b/Lib/argparse.py
index 9c710cef5b6aaa..0370e244bae6da 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -1516,7 +1516,7 @@ def _get_positional_kwargs(self, dest, **kwargs):
 
         # mark positional arguments as required if at least one is
         # always required
-        if kwargs.get('nargs') not in [OPTIONAL, ZERO_OR_MORE]:
+        if kwargs.get('nargs') not in [OPTIONAL, ZERO_OR_MORE, REMAINDER]:
             kwargs['required'] = True
         if kwargs.get('nargs') == ZERO_OR_MORE and 'default' not in kwargs:
             kwargs['required'] = True
@@ -1915,6 +1915,10 @@ def take_action(action, argument_strings, option_string=None):
             # error if this argument is not allowed with other previously
             # seen arguments, assuming that actions that use the default
             # value don't really count as "present"
+            if action.nargs in [REMAINDER]:
+                if argument_values == []:
+                    action.default = argument_values
+
             if argument_values is not action.default:
                 seen_non_default_actions.add(action)
                 for conflict_action in action_conflicts.get(action, []):
diff --git a/Misc/NEWS.d/next/Library/2020-05-06-14-31-07.bpo-40509.PgYRgH.rst b/Misc/NEWS.d/next/Library/2020-05-06-14-31-07.bpo-40509.PgYRgH.rst
new file mode 100644
index 00000000000000..3b27661e239069
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-05-06-14-31-07.bpo-40509.PgYRgH.rst
@@ -0,0 +1 @@
+Allow REMAINDER positional arguments in argparse mutually exclusive groups.