diff -r 829117ae2e55 Include/unicodeobject.h
--- a/Include/unicodeobject.h	Tue Jul 19 16:46:09 2016 -0500
+++ b/Include/unicodeobject.h	Fri Jul 22 02:33:46 2016 +1000
@@ -2073,6 +2073,10 @@
 
 PyAPI_FUNC(int) PyUnicode_IsIdentifier(PyObject *s);
 
+/* Returns -1 if the string is a valid identifier, otherwise the index of
+the first character that is illegal. 0 is returned for empty strings. */
+PyAPI_FUNC(int) _PyUnicode_FindNonIdentifier(PyObject *self);
+
 #ifndef Py_LIMITED_API
 /* Externally visible for str.strip(unicode) */
 PyAPI_FUNC(PyObject *) _PyUnicode_XStrip(
diff -r 829117ae2e55 Objects/unicodeobject.c
--- a/Objects/unicodeobject.c	Tue Jul 19 16:46:09 2016 -0500
+++ b/Objects/unicodeobject.c	Fri Jul 22 02:33:46 2016 +1000
@@ -11923,6 +11923,12 @@
 int
 PyUnicode_IsIdentifier(PyObject *self)
 {
+    return _PyUnicode_FindNonIdentifier(self) == -1;
+}
+
+int
+_PyUnicode_FindNonIdentifier(PyObject *self)
+{
     int kind;
     void *data;
     Py_ssize_t i;
@@ -11953,8 +11959,8 @@
 
     for (i = 1; i < PyUnicode_GET_LENGTH(self); i++)
         if (!_PyUnicode_IsXidContinue(PyUnicode_READ(kind, data, i)))
-            return 0;
-    return 1;
+            return i;
+    return -1;
 }
 
 PyDoc_STRVAR(isidentifier__doc__,
diff -r 829117ae2e55 Parser/parsetok.c
--- a/Parser/parsetok.c	Tue Jul 19 16:46:09 2016 -0500
+++ b/Parser/parsetok.c	Fri Jul 22 02:33:46 2016 +1000
@@ -320,7 +320,10 @@
         if (tok->buf != NULL) {
             size_t len;
             assert(tok->cur - tok->buf < INT_MAX);
-            err_ret->offset = (int)(tok->cur - tok->buf);
+            if (tok->start)
+                err_ret->offset = (int)(tok->start - tok->buf + 1);
+            else
+                err_ret->offset = (int)(tok->cur - tok->buf);
             len = tok->inp - tok->buf;
             err_ret->text = (char *) PyObject_MALLOC(len + 1);
             if (err_ret->text != NULL) {
diff -r 829117ae2e55 Parser/tokenizer.c
--- a/Parser/tokenizer.c	Tue Jul 19 16:46:09 2016 -0500
+++ b/Parser/tokenizer.c	Fri Jul 22 02:33:46 2016 +1000
@@ -1325,11 +1325,13 @@
         }
         return 0;
     }
-    result = PyUnicode_IsIdentifier(s);
+    result = _PyUnicode_FindNonIdentifier(s);
     Py_DECREF(s);
-    if (result == 0)
-        tok->done = E_IDENTIFIER;
-    return result;
+    if (result == -1)
+        return 1;
+    tok->done = E_IDENTIFIER;
+    tok->start += result + 1;
+    return 0;
 }
 #endif