Index: Include/abstract.h
===================================================================
--- Include/abstract.h	(Revision 53031)
+++ Include/abstract.h	(Arbeitskopie)
@@ -1215,6 +1215,16 @@
 
      /* Implemented as macro:
 
+     PyObject *PyMapping_IterKeys(PyObject *o);
+
+         On success, return an iterator of the keys in object o.  On
+	 failure, return NULL. This is equivalent to the Python
+	 expression: o.iterkeys().
+       */
+#define PyMapping_IterKeys(O) PyObject_CallMethod(O,"iterkeys",NULL)
+
+     /* Implemented as macro:
+
      PyObject *PyMapping_Keys(PyObject *o);
 
          On success, return a list of the keys in object o.  On
Index: Objects/dictobject.c
===================================================================
--- Objects/dictobject.c	(Revision 53031)
+++ Objects/dictobject.c	(Arbeitskopie)
@@ -1185,7 +1185,8 @@
 		result = -1;
 
 	else if (arg != NULL) {
-		if (PyObject_HasAttrString(arg, "keys"))
+		if (PyObject_HasAttrString(arg, "iterkeys") ||
+		    PyObject_HasAttrString(arg, "keys"))
 			result = PyDict_Merge(self, arg, 1);
 		else
 			result = PyDict_MergeFromSeq2(self, arg, 1);
@@ -1299,14 +1300,15 @@
 	/* We accept for the argument either a concrete dictionary object,
 	 * or an abstract "mapping" object.  For the former, we can do
 	 * things quite efficiently.  For the latter, we only require that
-	 * PyMapping_Keys() and PyObject_GetItem() be supported.
+	 * (PyMapping_IterKeys() or PyMapping_Keys()) and PyObject_GetItem()
+	 * be supported.
 	 */
 	if (a == NULL || !PyDict_Check(a) || b == NULL) {
 		PyErr_BadInternalCall();
 		return -1;
 	}
 	mp = (dictobject*)a;
-	if (PyDict_Check(b)) {
+	if (PyDict_CheckExact(b)) {
 		other = (dictobject*)b;
 		if (other == mp || other->ma_used == 0)
 			/* a.update(a) or a.update({}); nothing to do */
@@ -1341,21 +1343,24 @@
 	}
 	else {
 		/* Do it the generic, slower way */
-		PyObject *keys = PyMapping_Keys(b);
-		PyObject *iter;
+		PyObject *iter = PyMapping_IterKeys(b);
 		PyObject *key, *value;
 		int status;
 
-		if (keys == NULL)
-			/* Docstring says this is equivalent to E.keys() so
-			 * if E doesn't have a .keys() method we want
-			 * AttributeError to percolate up.  Might as well
-			 * do the same for any other error.
-			 */
-			return -1;
-
-		iter = PyObject_GetIter(keys);
-		Py_DECREF(keys);
+		if (iter == NULL) {
+			/* might be an old mapping without iterkeys() => try keys() */
+			PyErr_Clear();
+			PyObject *keys = PyMapping_Keys(b);
+			if (keys == NULL)
+				/* Docstring says this is equivalent to E.keys() so
+				 * if E doesn't have a .keys() method we want
+				 * AttributeError to percolate up.  Might as well
+				 * do the same for any other error.
+				 */
+				return -1;
+			iter = PyObject_GetIter(keys);
+			Py_DECREF(keys);
+		}
 		if (iter == NULL)
 			return -1;
 
Index: Lib/test/test_dict.py
===================================================================
--- Lib/test/test_dict.py	(Revision 53031)
+++ Lib/test/test_dict.py	(Arbeitskopie)
@@ -136,6 +136,17 @@
         d.update(SimpleUserDict())
         self.assertEqual(d, {1:1, 2:2, 3:3})
 
+        class SimpleIterUserDict:
+            def __init__(self):
+                self.d = {1:1, 2:2, 3:3}
+            def iterkeys(self):
+                return iter(self.d)
+            def __getitem__(self, i):
+                return self.d[i]
+        d.clear()
+        d.update(SimpleIterUserDict())
+        self.assertEqual(d, {1:1, 2:2, 3:3})
+
         class Exc(Exception): pass
 
         d.clear()