diff -r 265d35e8fe82 Lib/test/test_bisect.py
--- a/Lib/test/test_bisect.py	Fri Jan 27 21:17:04 2012 +0000
+++ b/Lib/test/test_bisect.py	Sat Jan 28 10:03:24 2012 +0000
@@ -122,6 +122,13 @@
         self.assertRaises(ValueError, mod.insort_left, [1, 2, 3], 5, -1, 3),
         self.assertRaises(ValueError, mod.insort_right, [1, 2, 3], 5, -1, 3),
 
+    def test_large_range(self):
+        # Issue 13496
+        mod = self.module
+        data = range(sys.maxsize-1)
+        self.assertEqual(mod.bisect_left(data, sys.maxsize-3), sys.maxsize-3)
+        self.assertEqual(mod.bisect_right(data, sys.maxsize-3), sys.maxsize-2)
+
     def test_random(self, n=25):
         from random import randrange
         for i in range(n):
diff -r 265d35e8fe82 Modules/_bisectmodule.c
--- a/Modules/_bisectmodule.c	Fri Jan 27 21:17:04 2012 +0000
+++ b/Modules/_bisectmodule.c	Sat Jan 28 10:03:24 2012 +0000
@@ -21,7 +21,7 @@
             return -1;
     }
     while (lo < hi) {
-        mid = (lo + hi) / 2;
+        mid = (lo + (size_t)hi) / 2;
         litem = PySequence_GetItem(list, mid);
         if (litem == NULL)
             return -1;
@@ -123,7 +123,7 @@
             return -1;
     }
     while (lo < hi) {
-        mid = (lo + hi) / 2;
+        mid = (lo + (size_t)hi) / 2;
         litem = PySequence_GetItem(list, mid);
         if (litem == NULL)
             return -1;