diff --git a/Lib/http/server.py b/Lib/http/server.py
index 94f730ed344..e985dfd5640 100644
--- a/Lib/http/server.py
+++ b/Lib/http/server.py
@@ -689,6 +689,7 @@ class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
                              parts[3], parts[4])
                 new_url = urllib.parse.urlunsplit(new_parts)
                 self.send_header("Location", new_url)
+                self.send_header("Content-Length", "0")
                 self.end_headers()
                 return None
             for index in "index.html", "index.htm":
diff --git a/Lib/test/test_httpservers.py b/Lib/test/test_httpservers.py
index 6b17817b22b..cb0a3aa9e40 100644
--- a/Lib/test/test_httpservers.py
+++ b/Lib/test/test_httpservers.py
@@ -428,6 +428,7 @@ class SimpleHTTPServerTestCase(BaseTestCase):
         self.check_status_and_reason(response, HTTPStatus.OK)
         response = self.request(self.base_url)
         self.check_status_and_reason(response, HTTPStatus.MOVED_PERMANENTLY)
+        self.assertEqual(response.getheader("Content-Length"), "0")
         response = self.request(self.base_url + '/?hi=2')
         self.check_status_and_reason(response, HTTPStatus.OK)
         response = self.request(self.base_url + '?hi=1')
diff --git a/Misc/NEWS.d/next/Library/2021-04-30-16-58-24.bpo-43972.Y2r9lg.rst b/Misc/NEWS.d/next/Library/2021-04-30-16-58-24.bpo-43972.Y2r9lg.rst
new file mode 100644
index 00000000000..3d67b885bab
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-04-30-16-58-24.bpo-43972.Y2r9lg.rst
@@ -0,0 +1,3 @@
+When :class:`http.server.SimpleHTTPRequestHandler` sends a
+``301 (Moved Permanently)`` for a directory path not ending with `/`, add a
+``Content-Length: 0`` header. This improves the behavior for certain clients.