diff --git a/django/template/context.py b/django/template/context.py
index bcfaa3bf9e..acc5758f75 100644
--- a/django/template/context.py
+++ b/django/template/context.py
@@ -14,21 +14,16 @@ class ContextPopException(Exception):
     "pop() has been called more times than push()"
     pass
 
-class EmptyClass(object):
-    # No-op class which takes no args to its __init__ method, to help implement
-    # __copy__
-    pass
-
 class BaseContext(object):
     def __init__(self, dict_=None):
-        dict_ = dict_ or {}
-        self.dicts = [dict_]
+        self._reset_dicts(dict_)
+
+    def _reset_dicts(self, value=None):
+        self.dicts = [value or {}]
 
     def __copy__(self):
-        duplicate = EmptyClass()
-        duplicate.__class__ = self.__class__
-        duplicate.__dict__ = self.__dict__.copy()
-        duplicate.dicts = duplicate.dicts[:]
+        duplicate = copy(super(BaseContext, self))
+        duplicate.dicts = self.dicts[:]
         return duplicate
 
     def __repr__(self):
@@ -78,6 +73,15 @@ class BaseContext(object):
                 return d[key]
         return otherwise
 
+    def new(self, values=None):
+        """
+        Returns a new context with the same properties, but with only the
+        values given in 'values' stored.
+        """
+        new_context = copy(self)
+        new_context._reset_dicts(values)
+        return new_context
+
 class Context(BaseContext):
     "A stack container for variable context"
     def __init__(self, dict_=None, autoescape=True, current_app=None, use_l10n=None):
@@ -88,7 +92,7 @@ class Context(BaseContext):
         super(Context, self).__init__(dict_)
 
     def __copy__(self):
-        duplicate = super(Context, self).__copy__()
+        duplicate = copy(super(Context, self))
         duplicate.render_context = copy(self.render_context)
         return duplicate
 
@@ -99,14 +103,6 @@ class Context(BaseContext):
         self.dicts.append(other_dict)
         return other_dict
 
-    def new(self, values=None):
-        """
-        Returns a new Context with the same 'autoescape' value etc, but with
-        only the values given in 'values' stored.
-        """
-        return self.__class__(dict_=values, autoescape=self.autoescape,
-                              current_app=self.current_app, use_l10n=self.use_l10n)
-
 class RenderContext(BaseContext):
     """
     A stack container for storing Template state.
diff --git a/tests/regressiontests/templates/tests.py b/tests/regressiontests/templates/tests.py
index a051d7335e..dedd7d5c92 100644
--- a/tests/regressiontests/templates/tests.py
+++ b/tests/regressiontests/templates/tests.py
@@ -1639,5 +1639,34 @@ class TemplateTagLoading(unittest.TestCase):
         settings.INSTALLED_APPS = ('tagsegg',)
         t = template.Template(ttext)
 
+
+class RequestContextTests(BaseTemplateResponseTest):
+
+    def setUp(self):
+        templates = {
+            'child': Template('{{ var|default:"none" }}'),
+        }
+        setup_test_template_loader(templates)
+        self.fake_request = RequestFactory().get('/')
+
+    def tearDown(self):
+        restore_template_loaders()
+
+    def test_include_only(self):
+        """
+        Regression test for #15721, ``{% include %}`` and ``RequestContext``
+        not playing together nicely.
+        """
+        ctx = RequestContext(self.fake_request, {'var': 'parent'})
+        self.assertEqual(
+            template.Template('{% include "child" %}').render(ctx),
+            'parent'
+        )
+        self.assertEqual(
+            template.Template('{% include "child" only %}').render(ctx),
+            'none'
+        )
+
+
 if __name__ == "__main__":
     unittest.main()