# HG changeset patch
# Parent 64485e0700baa09df15aa4075c2bbba588fd8305

diff --git a/Lib/unittest/case.py b/Lib/unittest/case.py
--- a/Lib/unittest/case.py
+++ b/Lib/unittest/case.py
@@ -1056,12 +1056,18 @@
             standardMsg = 'unexpectedly None'
             self.fail(self._formatMessage(msg, standardMsg))
 
-    def assertIsInstance(self, obj, cls, msg=None):
+    def assertIsInstance(self, obj, cls, msg=None, exact_type=None):
         """Same as self.assertTrue(isinstance(obj, cls)), with a nicer
         default message."""
         if not isinstance(obj, cls):
             standardMsg = '%s is not an instance of %r' % (safe_repr(obj), cls)
             self.fail(self._formatMessage(msg, standardMsg))
+        if exact_type:
+            if isinstance(exact_type, type):
+                cls = exact_type
+            if type(obj) is not cls:
+                standardMsg = 'type of %s is not %r' % (safe_repr(obj), cls)
+                self.fail(self._formatMessage(msg, standardMsg))
 
     def assertNotIsInstance(self, obj, cls, msg=None):
         """Included for symmetry with assertIsInstance."""
diff --git a/Lib/unittest/test/test_case.py b/Lib/unittest/test/test_case.py
--- a/Lib/unittest/test/test_case.py
+++ b/Lib/unittest/test/test_case.py
@@ -493,9 +493,17 @@
 
     def testAssertIsInstance(self):
         thing = []
+        Duck = type('Duck', (list,), {})
+        duck = Duck()
         self.assertIsInstance(thing, list)
+        self.assertIsInstance(thing, list, exact_type=True)
+        self.assertIsInstance(duck, list)
+        self.assertIsInstance(duck, list, exact_type=Duck)
+
         self.assertRaises(self.failureException, self.assertIsInstance,
                           thing, dict)
+        self.assertRaises(self.failureException, self.assertIsInstance,
+                          duck, list, exact_type=True)
 
     def testAssertNotIsInstance(self):
         thing = []