diff -r e392f1b88fff Modules/_elementtree.c
--- a/Modules/_elementtree.c	Mon May 20 10:28:48 2013 -0700
+++ b/Modules/_elementtree.c	Tue May 21 06:21:52 2013 +0300
@@ -3117,6 +3117,8 @@
 
     if (PyUnicode_GET_LENGTH(u) != 256) {
         Py_DECREF(u);
+        PyErr_SetString(PyExc_ValueError,
+                        "multi-byte encodings are not supported");
         return XML_STATUS_ERROR;
     }
 
diff -r e392f1b88fff Modules/pyexpat.c
--- a/Modules/pyexpat.c	Mon May 20 10:28:48 2013 -0700
+++ b/Modules/pyexpat.c	Tue May 21 06:21:52 2013 +0300
@@ -1129,7 +1129,6 @@
                          XML_Encoding *info)
 {
     PyUnicodeObject *_u_string = NULL;
-    int result = 0;
     int i;
     int kind;
     void *data;
@@ -1139,7 +1138,14 @@
         PyUnicode_Decode(template_buffer, 256, name, "replace");
 
     if (_u_string == NULL || PyUnicode_READY(_u_string) == -1)
-        return result;
+        return XML_STATUS_ERROR;
+
+    if (PyUnicode_GET_LENGTH(_u_string) != 256) {
+        Py_DECREF(_u_string);
+        PyErr_SetString(PyExc_ValueError,
+                        "multi-byte encodings are not supported");
+        return XML_STATUS_ERROR;
+    }
 
     kind = PyUnicode_KIND(_u_string);
     data = PyUnicode_DATA(_u_string);
@@ -1155,9 +1161,8 @@
     info->data = NULL;
     info->convert = NULL;
     info->release = NULL;
-    result = 1;
     Py_DECREF(_u_string);
-    return result;
+    return XML_STATUS_OK;
 }