diff -r 0bbf121c48c6 Lib/collections/__init__.py
--- a/Lib/collections/__init__.py	Wed Mar 25 19:16:54 2015 +0200
+++ b/Lib/collections/__init__.py	Wed Mar 25 20:42:03 2015 +0200
@@ -924,7 +924,23 @@ class ChainMap(MutableMapping):
 class UserDict(MutableMapping):
 
     # Start by filling-out the abstract methods
-    def __init__(self, dict=None, **kwargs):
+    def __init__(*args, **kwargs):
+        if not args:
+            raise TypeError("descriptor '__init__' of 'UserDict' object "
+                            "needs an argument")
+        self, *args = args
+        if len(args) > 1:
+            raise TypeError('expected at most 1 arguments, got %d' % len(args))
+        if args:
+            dict = args[0]
+        else:
+            if 'dict' in kwargs:
+                dict = kwargs.pop('dict')
+                import warnings
+                warnings.warn("Passing 'dict' as keyword argument is "
+                              "deprecated", DeprecationWarning, stacklevel=2)
+            else:
+                dict = None
         self.data = {}
         if dict is not None:
             self.update(dict)
diff -r 0bbf121c48c6 Lib/test/test_userdict.py
--- a/Lib/test/test_userdict.py	Wed Mar 25 19:16:54 2015 +0200
+++ b/Lib/test/test_userdict.py	Wed Mar 25 20:42:03 2015 +0200
@@ -2,6 +2,7 @@
 
 from test import support, mapping_tests
 import collections
+from collections import UserDict
 
 d0 = {}
 d1 = {"one": 1}
@@ -29,7 +30,8 @@ class UserDictTest(mapping_tests.TestHas
         self.assertEqual(collections.UserDict(one=1, two=2), d2)
         # item sequence constructor
         self.assertEqual(collections.UserDict([('one',1), ('two',2)]), d2)
-        self.assertEqual(collections.UserDict(dict=[('one',1), ('two',2)]), d2)
+        with support.check_warnings(('.*dict.*', DeprecationWarning)):
+            self.assertEqual(collections.UserDict(dict=[('one',1), ('two',2)]), d2)
         # both together
         self.assertEqual(collections.UserDict([('one',1), ('two',2)], two=3, three=5), d3)
 
@@ -139,6 +141,26 @@ class UserDictTest(mapping_tests.TestHas
         self.assertEqual(t.popitem(), ("x", 42))
         self.assertRaises(KeyError, t.popitem)
 
+    def test_init(self):
+        for kw in 'self', 'other', 'iterable':
+            self.assertEqual(list(UserDict(**{kw: 42}).items()), [(kw, 42)])
+        self.assertEqual(list(UserDict({}, dict=42).items()), [('dict', 42)])
+        self.assertEqual(list(UserDict({}, dict=None).items()), [('dict', None)])
+        with support.check_warnings(('.*dict.*', DeprecationWarning)):
+            self.assertEqual(list(UserDict(dict={'a': 42}).items()), [('a', 42)])
+        self.assertRaises(TypeError, UserDict, 42)
+        self.assertRaises(TypeError, UserDict, (), ())
+        self.assertRaises(TypeError, UserDict.__init__)
+
+    def test_update(self):
+        for kw in 'self', 'dict', 'other', 'iterable':
+            d = UserDict()
+            d.update(**{kw: 42})
+            self.assertEqual(list(d.items()), [(kw, 42)])
+        self.assertRaises(TypeError, UserDict().update, 42)
+        self.assertRaises(TypeError, UserDict().update, {}, {})
+        self.assertRaises(TypeError, UserDict.update)
+
     def test_missing(self):
         # Make sure UserDict doesn't have a __missing__ method
         self.assertEqual(hasattr(collections.UserDict, "__missing__"), False)