diff --git a/django/http/__init__.py b/django/http/__init__.py
index ded6d090b1..60b6d15795 100644
--- a/django/http/__init__.py
+++ b/django/http/__init__.py
@@ -211,8 +211,13 @@ class QueryDict(MultiValueDict):
     def update(self, other_dict):
         self._assert_mutable()
         f = lambda s: str_to_unicode(s, self.encoding)
-        d = dict([(f(k), f(v)) for k, v in other_dict.items()])
-        MultiValueDict.update(self, d)
+        if hasattr(other_dict, 'lists'):
+            for key, valuelist in other_dict.lists():
+                for value in valuelist:
+                    MultiValueDict.update(self, {f(key): f(value)})
+        else:
+            d = dict([(f(k), f(v)) for k, v in other_dict.items()])
+            MultiValueDict.update(self, d)
 
     def pop(self, key, *args):
         self._assert_mutable()
diff --git a/tests/regressiontests/httpwrappers/tests.py b/tests/regressiontests/httpwrappers/tests.py
index b10c24e7bf..844b356366 100644
--- a/tests/regressiontests/httpwrappers/tests.py
+++ b/tests/regressiontests/httpwrappers/tests.py
@@ -436,6 +436,14 @@ Traceback (most recent call last):
 ...
 UnicodeEncodeError: ..., HTTP response headers must be in US-ASCII format
 
+#
+# Regression test for #8278: QueryDict.update(QueryDict)
+#
+>>> x = QueryDict("a=1&a=2", mutable=True)
+>>> y = QueryDict("a=3&a=4")
+>>> x.update(y)
+>>> x.getlist('a')
+[u'1', u'2', u'3', u'4']
 """
 
 from django.http import QueryDict, HttpResponse