diff -r 22f2784a276e -r 5f0cddb01246 Lib/test/test_iter.py
--- a/Lib/test/test_iter.py	Fri Dec 05 10:18:30 2014 +0100
+++ b/Lib/test/test_iter.py	Sun Dec 07 21:54:17 2014 +0100
@@ -1,5 +1,6 @@
 # Test iterators.
 
+import sys
 import unittest
 from test.support import run_unittest, TESTFN, unlink, cpython_only
 import pickle
@@ -918,6 +919,31 @@
         lst.extend(gen())
         self.assertEqual(len(lst), 760)
 
+    @cpython_only
+    def test_iter_overflow(self):
+        # Test for the issue 22939
+        class X(object):
+            def __getitem__(self, index):
+                return index
+
+        it = iter(X())
+        # Manually set `it_index` to PY_SSIZE_T_MAX without a loop
+        it.__setstate__(sys.maxsize)
+        with self.assertRaises(OverflowError):
+            next(it)
+        # Check that Overflow error is always raised
+        with self.assertRaises(OverflowError):
+            next(it)
+
+    def test_iter_neg_setstate(self):
+        class X(object):
+            def __getitem__(self, index):
+                return index
+
+        it = iter(X())
+        it.__setstate__(-42)
+        self.assertEqual(next(it), 0)
+
 
 def test_main():
     run_unittest(TestCase)
diff -r 22f2784a276e -r 5f0cddb01246 Objects/iterobject.c
--- a/Objects/iterobject.c	Fri Dec 05 10:18:30 2014 +0100
+++ b/Objects/iterobject.c	Sun Dec 07 21:54:17 2014 +0100
@@ -54,6 +54,11 @@
     seq = it->it_seq;
     if (seq == NULL)
         return NULL;
+    if (it->it_index == PY_SSIZE_T_MAX) {
+        PyErr_SetString(PyExc_OverflowError,
+                        "iter index too large");
+        return NULL;
+    }
 
     result = PySequence_GetItem(seq, it->it_index);
     if (result != NULL) {