diff --git a/django/core/cache/backends/base.py b/django/core/cache/backends/base.py
index ff4223bf86..58e166d655 100644
--- a/django/core/cache/backends/base.py
+++ b/django/core/cache/backends/base.py
@@ -63,4 +63,11 @@ class BaseCache(object):
         """
         return self.get(key) is not None
 
-    __contains__ = has_key
+    def __contains__(self, key):
+        """
+        Returns True if the key is in the cache and has not expired.
+        """
+        # This is a separate method, rather than just a copy of has_key(),
+        # so that it always has the same functionality as has_key(), even
+        # if a subclass overrides it.
+        return self.has_key(key)
diff --git a/tests/regressiontests/cache/tests.py b/tests/regressiontests/cache/tests.py
index f050348c77..703fbe5534 100644
--- a/tests/regressiontests/cache/tests.py
+++ b/tests/regressiontests/cache/tests.py
@@ -56,11 +56,15 @@ class Cache(unittest.TestCase):
         cache.set("hello1", "goodbye1")
         self.assertEqual(cache.has_key("hello1"), True)
         self.assertEqual(cache.has_key("goodbye1"), False)
+        cache.set("empty", 'fred')
+        self.assertEqual(cache.has_key("empty"), True)
 
     def test_in(self):
         cache.set("hello2", "goodbye2")
         self.assertEqual("hello2" in cache, True)
         self.assertEqual("goodbye2" in cache, False)
+        cache.set("empty", 'fred')
+        self.assertEqual("empty" in cache, True)
 
     def test_data_types(self):
         stuff = {