diff --git a/AUTHORS b/AUTHORS
index c058559787..044391e4a3 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -908,6 +908,7 @@ answer newbie questions, and generally made Django that much better:
     Roel Delos Reyes <https://roelzkie.dev>
     Rohith P R <https://rohithpr.com>
     Romain Garrigues <romain.garrigues.cs@gmail.com>
+    Ronan LE HAY <ronan@le-hay.fr>
     Ronnie van den Crommenacker
     Ronny Haryanto <https://ronny.haryan.to/>
     Ross Poulton <ross@rossp.org>
diff --git a/django/middleware/common.py b/django/middleware/common.py
index bf22d00f01..870d462e6d 100644
--- a/django/middleware/common.py
+++ b/django/middleware/common.py
@@ -105,7 +105,9 @@ class CommonMiddleware(MiddlewareMixin):
         # If the given URL is "Not Found", then check if we should redirect to
         # a path with a slash appended.
         if response.status_code == 404 and self.should_redirect_with_slash(request):
-            return self.response_redirect_class(self.get_full_path_with_slash(request))
+            response = self.response_redirect_class(
+                self.get_full_path_with_slash(request)
+            )
 
         # Add the Content-Length header to non-streaming responses if not
         # already set.
diff --git a/tests/middleware/tests.py b/tests/middleware/tests.py
index 2e796ecfc7..c4aac0552b 100644
--- a/tests/middleware/tests.py
+++ b/tests/middleware/tests.py
@@ -350,6 +350,19 @@ class CommonMiddlewareTest(SimpleTestCase):
         response = CommonMiddleware(get_response)(self.rf.get("/"))
         self.assertEqual(int(response.headers["Content-Length"]), bad_content_length)
 
+    @override_settings(APPEND_SLASH=True)
+    def test_content_length_header_added_to_append_slash_redirect(self):
+        """
+        The Content-Length header is set when redirecting with the APPEND_SLASH
+        setting.
+        """
+        request = self.rf.get("/customurlconf/slash")
+        request.urlconf = "middleware.extra_urls"
+        r = CommonMiddleware(get_response_404)(request)
+        self.assertEqual(r.status_code, 301)
+        self.assertEqual(r.url, "/customurlconf/slash/")
+        self.assertTrue(r.has_header("Content-Length"))
+
     # Other tests
 
     @override_settings(DISALLOWED_USER_AGENTS=[re.compile(r"foo")])