diff --git a/django/http/__init__.py b/django/http/__init__.py
index 68ac45d6e3..07e5a46797 100644
--- a/django/http/__init__.py
+++ b/django/http/__init__.py
@@ -92,7 +92,7 @@ else:
         if not _cookie_allows_colon_in_names:
             def load(self, rawdata, ignore_parse_errors=False):
                 if ignore_parse_errors:
-                    self.bad_cookies = []
+                    self.bad_cookies = set()
                     self._BaseCookie__set = self._loose_set
                 super(SimpleCookie, self).load(rawdata)
                 if ignore_parse_errors:
@@ -106,8 +106,8 @@ else:
                 try:
                     self._strict_set(key, real_value, coded_value)
                 except Cookie.CookieError:
-                    self.bad_cookies.append(key)
-                    dict.__setitem__(self, key, None)
+                    self.bad_cookies.add(key)
+                    dict.__setitem__(self, key, Cookie.Morsel())
 
 
 class CompatCookie(SimpleCookie):
diff --git a/tests/regressiontests/httpwrappers/tests.py b/tests/regressiontests/httpwrappers/tests.py
index 2e2932f0cf..6aabfe655e 100644
--- a/tests/regressiontests/httpwrappers/tests.py
+++ b/tests/regressiontests/httpwrappers/tests.py
@@ -281,3 +281,9 @@ class CookieTests(unittest.TestCase):
         Test that a single non-standard cookie name doesn't affect all cookies. Ticket #13007.
         """
         self.assertTrue('good_cookie' in parse_cookie('good_cookie=yes;bad:cookie=yes').keys())
+
+    def test_repeated_nonstandard_keys(self):
+        """
+        Test that a repeated non-standard name doesn't affect all cookies. Ticket #15852
+        """
+        self.assertTrue('good_cookie' in parse_cookie('a,=b; a,=c; good_cookie=yes').keys())