diff --git a/django/views/debug.py b/django/views/debug.py
index ac81ecaf9e..23bf16604d 100644
--- a/django/views/debug.py
+++ b/django/views/debug.py
@@ -33,6 +33,19 @@ def linebreak_iter(template_source):
     yield len(template_source) + 1
 
 
+class CallableSettingWrapper(object):
+    """ Object to wrap callable appearing in settings
+
+    * Not to call in the debug page (#21345).
+    * Not to break the debug page if the callable forbidding to set attributes (#23070).
+    """
+    def __init__(self, callable_setting):
+        self._wrapped = callable_setting
+
+    def __repr__(self):
+        return repr(self._wrapped)
+
+
 def cleanse_setting(key, value):
     """Cleanse an individual setting key/value of sensitive content.
 
@@ -52,7 +65,8 @@ def cleanse_setting(key, value):
         cleansed = value
 
     if callable(cleansed):
-        cleansed.do_not_call_in_templates = True
+        # For fixing #21345 and #23070
+        cleansed = CallableSettingWrapper(cleansed)
 
     return cleansed
 
diff --git a/tests/view_tests/tests/test_debug.py b/tests/view_tests/tests/test_debug.py
index 7d800ae591..3d51da9f94 100644
--- a/tests/view_tests/tests/test_debug.py
+++ b/tests/view_tests/tests/test_debug.py
@@ -20,7 +20,7 @@ from django.test import TestCase, RequestFactory, override_settings
 from django.test.utils import override_with_test_loader
 from django.utils.encoding import force_text, force_bytes
 from django.utils import six
-from django.views.debug import ExceptionReporter
+from django.views.debug import CallableSettingWrapper, ExceptionReporter
 
 from .. import BrokenException, except_args
 from ..views import (sensitive_view, non_sensitive_view, paranoid_view,
@@ -29,6 +29,21 @@ from ..views import (sensitive_view, non_sensitive_view, paranoid_view,
     multivalue_dict_key_error)
 
 
+class CallableSettingWrapperTests(TestCase):
+    """ Unittests for CallableSettingWrapper
+    """
+    def test_repr(self):
+        class WrappedCallable(object):
+            def __repr__(self):
+                return "repr from the wrapped callable"
+
+            def __call__(self):
+                pass
+
+        actual = repr(CallableSettingWrapper(WrappedCallable()))
+        self.assertEqual(actual, "repr from the wrapped callable")
+
+
 @override_settings(DEBUG=True, TEMPLATE_DEBUG=True,
                    ROOT_URLCONF="view_tests.urls")
 class DebugViewTests(TestCase):
@@ -660,6 +675,21 @@ class ExceptionReporterFilterTests(TestCase, ExceptionReportTestMixin):
             response = self.client.get('/raises500/')
             self.assertNotContains(response, "This should not be displayed", status_code=500)
 
+    def test_callable_settings_forbidding_to_set_attributes(self):
+        """
+        Callable settings which forbid to set attributes should not break
+        the debug page (#23070).
+        """
+        class CallableSettingWithSlots(object):
+            __slots__ = []
+
+            def __call__(self):
+                return "This should not be displayed"
+
+        with self.settings(DEBUG=True, WITH_SLOTS=CallableSettingWithSlots()):
+            response = self.client.get('/raises500/')
+            self.assertNotContains(response, "This should not be displayed", status_code=500)
+
     def test_dict_setting_with_non_str_key(self):
         """
         A dict setting containing a non-string key should not break the