diff --git a/Lib/json/tests/test_scanstring.py b/Lib/json/tests/test_scanstring.py
index 2d55672b7ad..2e9136b08f9 100644
--- a/Lib/json/tests/test_scanstring.py
+++ b/Lib/json/tests/test_scanstring.py
@@ -102,3 +102,6 @@ class TestScanString(TestCase):
         self.assertEquals(
             scanstring('["Bad value", truth]', 2, True),
             ('Bad value', 12))
+
+    def test_overflow(self):
+        self.assertRaises(OverflowError, json.decoder.scanstring, b"xxx", sys.maxsize+1)
diff --git a/Modules/_json.c b/Modules/_json.c
index 45f4b58e41d..c44dbac1f13 100644
--- a/Modules/_json.c
+++ b/Modules/_json.c
@@ -133,9 +133,9 @@ _convertPyInt_AsSsize_t(PyObject *o, Py_ssize_t *size_ptr)
 {
     /* PyObject to Py_ssize_t converter */
     *size_ptr = PyLong_AsSsize_t(o);
-    if (*size_ptr == -1 && PyErr_Occurred());
-        return 1;
-    return 0;
+    if (*size_ptr == -1 && PyErr_Occurred())
+        return 0;
+    return 1;
 }
 
 static PyObject *