diff --git a/Lib/argparse.py b/Lib/argparse.py
index 02e98bbf920cf1..4be276811cbe61 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -1548,7 +1548,7 @@ def _get_positional_kwargs(self, dest, **kwargs):
             kwargs['required'] = True
 
         # return the keyword arguments with no option strings
-        return dict(kwargs, dest=dest, option_strings=[])
+        return dict(kwargs, dest=dest.replace("-", "_"), option_strings=[])
 
     def _get_optional_kwargs(self, *args, **kwargs):
         # determine short and long option strings
diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
index 425b6bb3e0b4ee..97ae6f612df798 100644
--- a/Lib/test/test_argparse.py
+++ b/Lib/test/test_argparse.py
@@ -923,6 +923,22 @@ class TestDisallowLongAbbreviationAllowsShortGroupingPrefix(ParserTestCase):
 # Positional tests
 # ================
 
+
+class TestPositionalsDest(ParserTestCase):
+    """Test a Positional containing - is converted to _ in the resulting namepsace"""
+
+    argument_signatures = [Sig('foo-bar')]
+
+    failures = []
+
+    successes = [
+
+        ('abc', NS(foo_bar='abc')),
+
+        ('def', NS(foo_bar='def'))
+
+    ]
+
 class TestPositionalsNargsNone(ParserTestCase):
     """Test a Positional that doesn't specify nargs"""