diff -r 26200f535296 Lib/test/test_capi.py
--- a/Lib/test/test_capi.py	Wed Oct 03 13:53:28 2012 +0530
+++ b/Lib/test/test_capi.py	Thu Oct 04 09:26:56 2012 +0300
@@ -316,6 +316,17 @@
                     c, i, when_skipped, when_not_skipped))
             self.assertIs(when_skipped, when_not_skipped, message)
 
+    def test_parse_tuple_and_keywords(self):
+        # parse_tuple_and_keywords error handling tests
+        self.assertRaises(TypeError, _testcapi.parse_tuple_and_keywords,
+                          (), {}, 42, [])
+        self.assertRaises(ValueError, _testcapi.parse_tuple_and_keywords,
+                          (), {}, b'', 42)
+        self.assertRaises(ValueError, _testcapi.parse_tuple_and_keywords,
+                          (), {}, b'', [''] * 42)
+        self.assertRaises(ValueError, _testcapi.parse_tuple_and_keywords,
+                          (), {}, b'', [42])
+
 def test_main():
     support.run_unittest(CAPITest, TestPendingCalls,
                          Test6012, EmbeddingTest, SkipitemTest)
diff -r 26200f535296 Modules/_testcapimodule.c
--- a/Modules/_testcapimodule.c	Wed Oct 03 13:53:28 2012 +0530
+++ b/Modules/_testcapimodule.c	Thu Oct 04 09:26:56 2012 +0300
@@ -1238,7 +1238,7 @@
         o = PySequence_Fast_GET_ITEM(sub_keywords, i);
         if (!PyUnicode_FSConverter(o, (void *)(converted + i))) {
             PyErr_Format(PyExc_ValueError,
-                "parse_tuple_and_keywords: could not convert keywords[%s] to narrow string", i);
+                "parse_tuple_and_keywords: could not convert keywords[%zd] to narrow string", i);
             goto exit;
         }
         keywords[i] = PyBytes_AS_STRING(converted[i]);