diff --git a/django/utils/datastructures.py b/django/utils/datastructures.py
index 6aef313d351..cecb4da170e 100644
--- a/django/utils/datastructures.py
+++ b/django/utils/datastructures.py
@@ -14,6 +14,9 @@ class MergeDict(object):
                 pass
         raise KeyError
 
+    def __contains__(self, key):
+        return self.has_key(key)
+
     def get(self, key, default):
         try:
             return self[key]