diff -r aa079dc20555 src/org/python/core/PyString.java
--- a/src/org/python/core/PyString.java	Sat May 11 19:28:25 2013 +0100
+++ b/src/org/python/core/PyString.java	Sun May 12 01:00:21 2013 +0300
@@ -228,7 +228,7 @@
                 continue;
             }
                 /* Map UTF-16 surrogate pairs to Unicode \UXXXXXXXX escapes */
-                else if (ch >= 0xD800 && ch < 0xDC00) {
+                else if (ch >= 0xD800 && ch < 0xDC00 && i < str.length()) {
                     char ch2 = str.charAt(i++);
                     size--;
                     if (ch2 >= 0xDC00 && ch2 <= 0xDFFF) {