diff -r 7b076911f5f9 Lib/unittest/case.py
--- a/Lib/unittest/case.py	Fri Aug 31 17:15:49 2012 -0400
+++ b/Lib/unittest/case.py	Sat Sep 01 03:37:14 2012 +0100
@@ -94,12 +94,26 @@
         raise _UnexpectedSuccess
     return wrapper
 
+def _ensure_is_exception_type(e):
+    if isinstance(e, types.ClassType):
+        return
+    if not isinstance(e, type) or not issubclass(e, BaseException):
+        raise TypeError('assertRaises arg 1 must be an exception type '
+                        'or tuple of exception types')
+
 
 class _AssertRaisesContext(object):
     """A context manager used to implement TestCase.assertRaises* methods."""
 
     def __init__(self, expected, test_case, expected_regexp=None):
         self.expected = expected
+
+        if type(expected) is tuple:
+            for e in expected:
+                _ensure_is_exception_type(e)
+        else:
+            _ensure_is_exception_type(expected)
+
         self.failureException = test_case.failureException
         self.expected_regexp = expected_regexp
 
diff -r 7b076911f5f9 Lib/unittest/test/test_case.py
--- a/Lib/unittest/test/test_case.py	Fri Aug 31 17:15:49 2012 -0400
+++ b/Lib/unittest/test/test_case.py	Sat Sep 01 03:37:14 2012 +0100
@@ -1014,6 +1014,38 @@
         self.assertIsInstance(e, ExceptionMock)
         self.assertEqual(e.args[0], v)
 
+    def testAssertRaisesNoExceptionType(self):
+        try:
+            self.assertRaises(1)
+            self.fail("Expected TypeError")
+        except TypeError:
+            pass
+
+        try:
+            self.assertRaises(object)
+            self.fail("Expected TypeError")
+        except TypeError:
+            pass
+
+        try:
+            self.assertRaises((TypeError, 1))
+            self.fail("Expected TypeError")
+        except TypeError:
+            pass
+
+        try:
+            self.assertRaises((object, 1))
+            self.fail("Expected TypeError")
+        except TypeError:
+            pass
+
+        class _OldStyleError():
+            pass
+        def raises():
+            raise _OldStyleError()
+        self.assertRaises(_OldStyleError, raises)
+
+
     def testSynonymAssertMethodNames(self):
         """Test undocumented method name synonyms.
 
diff -r 7b076911f5f9 Misc/ACKS
--- a/Misc/ACKS	Fri Aug 31 17:15:49 2012 -0400
+++ b/Misc/ACKS	Sat Sep 01 03:37:14 2012 +0100
@@ -905,6 +905,7 @@
 Norman Vine
 Frank Visser
 Johannes Vogel
+Daniel Wagner-Hall
 Niki W. Waibel
 Wojtek Walczak
 Charles Waldman