diff -r 6234f4caba57 Include/unicodeobject.h
--- a/Include/unicodeobject.h	Tue May 06 11:42:37 2014 -0500
+++ b/Include/unicodeobject.h	Tue May 06 17:32:23 2014 -0400
@@ -2008,7 +2008,10 @@
     );
 
 #ifndef Py_LIMITED_API
-PyAPI_FUNC(int) _PyUnicode_CompareWithId(
+/* Compare two strings and return 1 for equal, 0 for not equal
+ * Raise an exception and return -1 on error. */
+
+PyAPI_FUNC(int) _PyUnicode_CompareWithIdEqual(
     PyObject *left,             /* Left string */
     _Py_Identifier *right       /* Right identifier */
     );
diff -r 6234f4caba57 Objects/typeobject.c
--- a/Objects/typeobject.c	Tue May 06 11:42:37 2014 -0500
+++ b/Objects/typeobject.c	Tue May 06 17:32:23 2014 -0400
@@ -822,7 +822,7 @@
         return NULL;
     }
 
-    if (mod != NULL && _PyUnicode_CompareWithId(mod, &PyId_builtins))
+    if (mod != NULL && !_PyUnicode_CompareWithIdEqual(mod, &PyId_builtins))
         rtn = PyUnicode_FromFormat("<class '%U.%U'>", mod, name);
     else
         rtn = PyUnicode_FromFormat("<class '%s'>", type->tp_name);
@@ -2253,7 +2253,7 @@
             if (!valid_identifier(tmp))
                 goto error;
             assert(PyUnicode_Check(tmp));
-            if (_PyUnicode_CompareWithId(tmp, &PyId___dict__) == 0) {
+            if (_PyUnicode_CompareWithIdEqual(tmp, &PyId___dict__) > 0) {
                 if (!may_add_dict || add_dict) {
                     PyErr_SetString(PyExc_TypeError,
                         "__dict__ slot disallowed: "
@@ -2284,7 +2284,7 @@
         for (i = j = 0; i < nslots; i++) {
             tmp = PyTuple_GET_ITEM(slots, i);
             if ((add_dict &&
-                 _PyUnicode_CompareWithId(tmp, &PyId___dict__) == 0) ||
+                 _PyUnicode_CompareWithIdEqual(tmp, &PyId___dict__) > 0) ||
                 (add_weak &&
                  PyUnicode_CompareWithASCIIString(tmp, "__weakref__") == 0))
                 continue;
@@ -3311,7 +3311,7 @@
         Py_XDECREF(mod);
         return NULL;
     }
-    if (mod != NULL && _PyUnicode_CompareWithId(mod, &PyId_builtins))
+    if (mod != NULL && !_PyUnicode_CompareWithIdEqual(mod, &PyId_builtins))
         rtn = PyUnicode_FromFormat("<%U.%U object at %p>", mod, name, self);
     else
         rtn = PyUnicode_FromFormat("<%s object at %p>",
@@ -6763,7 +6763,7 @@
            (i.e. super, or a subclass), not the class of su->obj. */
         skip = (PyUnicode_Check(name) &&
                 PyUnicode_GET_LENGTH(name) == 9 &&
-                _PyUnicode_CompareWithId(name, &PyId___class__) == 0);
+                _PyUnicode_CompareWithIdEqual(name, &PyId___class__) > 0);
     }
 
     if (!skip) {
@@ -6969,7 +6969,7 @@
         for (i = 0; i < n; i++) {
             PyObject *name = PyTuple_GET_ITEM(co->co_freevars, i);
             assert(PyUnicode_Check(name));
-            if (!_PyUnicode_CompareWithId(name, &PyId___class__)) {
+            if (_PyUnicode_CompareWithIdEqual(name, &PyId___class__) > 0) {
                 Py_ssize_t index = co->co_nlocals +
                     PyTuple_GET_SIZE(co->co_cellvars) + i;
                 PyObject *cell = f->f_localsplus[index];
diff -r 6234f4caba57 Objects/unicodeobject.c
--- a/Objects/unicodeobject.c	Tue May 06 11:42:37 2014 -0500
+++ b/Objects/unicodeobject.c	Tue May 06 17:32:23 2014 -0400
@@ -10787,12 +10787,23 @@
 }
 
 int
-_PyUnicode_CompareWithId(PyObject *left, _Py_Identifier *right)
-{
-    PyObject *right_str = _PyUnicode_FromId(right);   /* borrowed */
-    if (right_str == NULL)
-        return -1;
-    return PyUnicode_Compare(left, right_str);
+_PyUnicode_CompareWithIdEqual(PyObject *left, _Py_Identifier *right)
+{
+    if (PyUnicode_Check(left)) {
+        PyObject *right_str = _PyUnicode_FromId(right); /* borrowed */
+        if (right_str == NULL)
+            return -1;
+        /* If left side is interned, then reference equality suffices */
+        if (PyUnicode_CHECK_INTERNED(left))
+            return left == right_str;
+        if (PyUnicode_READY(left) == -1)
+            return -1;
+        return unicode_compare_eq(left, right_str);
+    }
+    PyErr_Format(PyExc_TypeError,
+                 "Can't compare %.100s and str",
+                 left->ob_type->tp_name);
+    return -1;
 }
 
 int
diff -r 6234f4caba57 Python/errors.c
--- a/Python/errors.c	Tue May 06 11:42:37 2014 -0500
+++ b/Python/errors.c	Tue May 06 17:32:23 2014 -0400
@@ -908,7 +908,7 @@
             goto done;
     }
     else {
-        if (_PyUnicode_CompareWithId(moduleName, &PyId_builtins) != 0) {
+        if (_PyUnicode_CompareWithIdEqual(moduleName, &PyId_builtins) == 0) {
             if (PyFile_WriteObject(moduleName, f, Py_PRINT_RAW) < 0)
                 goto done;
             if (PyFile_WriteString(".", f) < 0)
diff -r 6234f4caba57 Python/pythonrun.c
--- a/Python/pythonrun.c	Tue May 06 11:42:37 2014 -0500
+++ b/Python/pythonrun.c	Tue May 06 17:32:23 2014 -0400
@@ -1965,7 +1965,7 @@
             err = PyFile_WriteString("<unknown>", f);
         }
         else {
-            if (_PyUnicode_CompareWithId(moduleName, &PyId_builtins) != 0)
+            if (_PyUnicode_CompareWithIdEqual(moduleName, &PyId_builtins) == 0)
             {
                 err = PyFile_WriteObject(moduleName, f, Py_PRINT_RAW);
                 err += PyFile_WriteString(".", f);