diff --git a/django/http/__init__.py b/django/http/__init__.py
index 7ded5546651..4b8f70fb4b6 100644
--- a/django/http/__init__.py
+++ b/django/http/__init__.py
@@ -683,7 +683,7 @@ class HttpResponse(object):
     def tell(self):
         if self._base_content_is_iter:
             raise Exception("This %s instance cannot tell its position" % self.__class__)
-        return sum([len(str(chunk)) for chunk in self._container])
+        return sum([len(chunk) for chunk in self])
 
 class HttpResponseRedirect(HttpResponse):
     status_code = 302
diff --git a/tests/regressiontests/httpwrappers/tests.py b/tests/regressiontests/httpwrappers/tests.py
index cc55057d31a..9b599db6d0e 100644
--- a/tests/regressiontests/httpwrappers/tests.py
+++ b/tests/regressiontests/httpwrappers/tests.py
@@ -1,3 +1,4 @@
+# -*- encoding: utf-8 -*-
 from __future__ import unicode_literals
 
 import copy
@@ -298,6 +299,17 @@ class HttpResponseTests(unittest.TestCase):
         self.assertRaises(UnicodeEncodeError,
                           getattr, r, 'content')
 
+    def test_file_interface(self):
+        r = HttpResponse()
+        r.write(b"hello")
+        self.assertEqual(r.tell(), 5)
+        r.write("привет")
+        self.assertEqual(r.tell(), 17)
+
+        r = HttpResponse(['abc'])
+        self.assertRaises(Exception, r.write, 'def')
+
+
 class CookieTests(unittest.TestCase):
     def test_encode(self):
         """