diff --git a/Lib/argparse.py b/Lib/argparse.py
index d4b6fb53af8..acd3154e681 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -2223,7 +2223,8 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
             if not self._has_negative_number_optionals:
                 return None
 
-        # if it contains a space (before any equal sign), it was meant to be a positional
+        # if it contains a space (before any equal sign), it was meant to be a
+        # positional
         if ' ' in arg_string.split("=", 1)[0]:
             return None
 
diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
index 60a18b00806..f378606cdec 100644
--- a/Lib/test/test_argparse.py
+++ b/Lib/test/test_argparse.py
@@ -2022,7 +2022,7 @@ class TestAddSubparsers(TestCase):
             self.parser.parse_known_args(['0.5', '--opt="with space"']),
             (NS(foo=False, bar=0.5), ['--opt="with space"']),
         )
-        self.assertRaisesRegexp(
+        self.assertRaisesRegex(
             ArgumentParserError,
             "invalid choice: '--opt with space'",
             self.parser.parse_known_args,
diff --git a/Misc/NEWS.d/next/Library/2020-07-06-15-25-29.bpo-22433.JBnwdX.rst b/Misc/NEWS.d/next/Library/2020-07-06-15-25-29.bpo-22433.JBnwdX.rst
new file mode 100644
index 00000000000..aa0adb5a732
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-07-06-15-25-29.bpo-22433.JBnwdX.rst
@@ -0,0 +1,2 @@
+Fixed handling of "--foo='bar baz'" as non-positional argument with
+:mod:`argparse`.