diff -r da3badae1765 Lib/json/decoder.py
--- a/Lib/json/decoder.py	Thu Oct 04 02:59:09 2012 +0200
+++ b/Lib/json/decoder.py	Thu Oct 04 19:46:32 2012 +0300
@@ -196,8 +196,8 @@
 
         try:
             value, end = scan_once(s, end)
-        except StopIteration:
-            raise ValueError(errmsg("Expecting object", s, end))
+        except StopIteration as err:
+            raise ValueError(errmsg("Expecting value", s, err.value)) from None
         pairs_append((key, value))
         try:
             nextchar = s[end]
@@ -240,8 +240,8 @@
     while True:
         try:
             value, end = scan_once(s, end)
-        except StopIteration:
-            raise ValueError(errmsg("Expecting object", s, end))
+        except StopIteration as err:
+            raise ValueError(errmsg("Expecting value", s, err.value)) from None
         _append(value)
         nextchar = s[end:end + 1]
         if nextchar in _ws:
@@ -366,6 +366,6 @@
         """
         try:
             obj, end = self.scan_once(s, idx)
-        except StopIteration:
-            raise ValueError("No JSON object could be decoded")
+        except StopIteration as err:
+            raise ValueError(errmsg("Expecting value", s, err.value)) from None
         return obj, end
diff -r da3badae1765 Lib/json/scanner.py
--- a/Lib/json/scanner.py	Thu Oct 04 02:59:09 2012 +0200
+++ b/Lib/json/scanner.py	Thu Oct 04 19:46:32 2012 +0300
@@ -29,7 +29,7 @@
         try:
             nextchar = string[idx]
         except IndexError:
-            raise StopIteration
+            raise StopIteration(idx)
 
         if nextchar == '"':
             return parse_string(string, idx + 1, strict)
@@ -60,7 +60,7 @@
         elif nextchar == '-' and string[idx:idx + 9] == '-Infinity':
             return parse_constant('-Infinity'), idx + 9
         else:
-            raise StopIteration
+            raise StopIteration(idx)
 
     def scan_once(string, idx):
         try:
diff -r da3badae1765 Modules/_json.c
--- a/Modules/_json.c	Thu Oct 04 02:59:09 2012 +0200
+++ b/Modules/_json.c	Thu Oct 04 19:46:32 2012 +0300
@@ -273,6 +273,16 @@
     }
 }
 
+static void
+raise_stop_iteration(Py_ssize_t idx)
+{
+    PyObject *value = PyLong_FromSsize_t(idx);
+    if (value != NULL) {
+        PyErr_SetObject(PyExc_StopIteration, value);
+        Py_DECREF(value);
+    }
+}
+
 static PyObject *
 _build_rval_index_tuple(PyObject *rval, Py_ssize_t idx) {
     /* return (rval, idx) tuple, stealing reference to rval */
@@ -877,7 +887,7 @@
     if (PyUnicode_READ(kind, str, idx) == '-') {
         idx++;
         if (idx > end_idx) {
-            PyErr_SetNone(PyExc_StopIteration);
+            raise_stop_iteration(start);
             return NULL;
         }
     }
@@ -893,7 +903,7 @@
     }
     /* no integer digits, error */
     else {
-        PyErr_SetNone(PyExc_StopIteration);
+        raise_stop_iteration(start);
         return NULL;
     }
 
@@ -986,7 +996,7 @@
     length = PyUnicode_GET_LENGTH(pystr);
 
     if (idx >= length) {
-        PyErr_SetNone(PyExc_StopIteration);
+        raise_stop_iteration(idx);
         return NULL;
     }