diff -r c6e0c29913ec Lib/unittest/mock.py
--- a/Lib/unittest/mock.py	Thu Sep 03 15:35:33 2015 -0700
+++ b/Lib/unittest/mock.py	Fri Sep 04 16:36:11 2015 +1200
@@ -2005,8 +2005,7 @@
             else:
                 other_args = ()
                 other_kwargs = value
-        else:
-            # len 2
+        elif len_other == 2:
             # could be (name, args) or (name, kwargs) or (args, kwargs)
             first, second = other
             if isinstance(first, str):
@@ -2017,6 +2016,8 @@
                     other_args, other_kwargs = (), second
             else:
                 other_args, other_kwargs = first, second
+        else:
+            return False
 
         if self_name and other_name != self_name:
             return False
diff -r c6e0c29913ec Lib/unittest/test/testmock/testmock.py
--- a/Lib/unittest/test/testmock/testmock.py	Thu Sep 03 15:35:33 2015 -0700
+++ b/Lib/unittest/test/testmock/testmock.py	Fri Sep 04 16:36:11 2015 +1200
@@ -299,7 +299,9 @@
         ])
         self.assertEqual(mock.call_args,
                          ((sentinel.Arg,), {"kw": sentinel.Kwarg}))
-
+        # Comparing call_args to a long sequence should not raise
+        # an exception. See issue 24857.
+        self.assertFalse(mock.call_args == "a long sequence")
 
     def test_assert_called_with(self):
         mock = Mock()