diff -r 568019d6bf6b Include/unicodeobject.h
--- a/Include/unicodeobject.h	Sat Dec 22 14:57:16 2012 +0100
+++ b/Include/unicodeobject.h	Sun Dec 23 18:19:57 2012 +0200
@@ -737,12 +737,13 @@
     Py_ssize_t end);
 
 #ifndef Py_LIMITED_API
-/* Compute the maximum character of the substring unicode[start:end].
-   Return 127 for an empty string. */
+/* Compute the maximum character of the substring unicode[start:end] and
+   maxchar. */
 PyAPI_FUNC(Py_UCS4) _PyUnicode_FindMaxChar (
     PyObject *unicode,
     Py_ssize_t start,
-    Py_ssize_t end);
+    Py_ssize_t end,
+    Py_UCS4 maxchar);
 #endif
 
 /* Copy the string into a UCS4 buffer including the null character if copy_null
diff -r 568019d6bf6b Objects/stringlib/unicode_format.h
--- a/Objects/stringlib/unicode_format.h	Sat Dec 22 14:57:16 2012 +0100
+++ b/Objects/stringlib/unicode_format.h	Sun Dec 23 18:19:57 2012 +0200
@@ -887,7 +887,8 @@
         sublen = literal.end - literal.start;
         if (sublen) {
             maxchar = _PyUnicode_FindMaxChar(literal.str,
-                                             literal.start, literal.end);
+                                             literal.start, literal.end,
+                                             writer->maxchar);
             err = _PyUnicodeWriter_Prepare(writer, sublen, maxchar);
             if (err == -1)
                 return 0;
diff -r 568019d6bf6b Objects/unicodeobject.c
--- a/Objects/unicodeobject.c	Sat Dec 22 14:57:16 2012 +0100
+++ b/Objects/unicodeobject.c	Sun Dec 23 18:19:57 2012 +0200
@@ -2002,7 +2002,8 @@
 }
 
 Py_UCS4
-_PyUnicode_FindMaxChar(PyObject *unicode, Py_ssize_t start, Py_ssize_t end)
+_PyUnicode_FindMaxChar(PyObject *unicode, Py_ssize_t start, Py_ssize_t end,
+                       Py_UCS4 maxchar)
 {
     enum PyUnicode_Kind kind;
     void *startptr, *endptr;
@@ -2013,13 +2014,16 @@
     assert(start <= end);
 
     if (start == 0 && end == PyUnicode_GET_LENGTH(unicode))
-        return PyUnicode_MAX_CHAR_VALUE(unicode);
+        return MAX_MAXCHAR(maxchar, PyUnicode_MAX_CHAR_VALUE(unicode));
 
     if (start == end)
-        return 127;
+        return maxchar;
 
     if (PyUnicode_IS_ASCII(unicode))
-        return 127;
+        return maxchar;
+
+    if (maxchar >= PyUnicode_MAX_CHAR_VALUE(unicode))
+        return maxchar;
 
     kind = PyUnicode_KIND(unicode);
     startptr = PyUnicode_DATA(unicode);
@@ -2027,11 +2031,11 @@
     startptr = (char *)startptr + start * kind;
     switch(kind) {
     case PyUnicode_1BYTE_KIND:
-        return ucs1lib_find_max_char(startptr, endptr);
+        return MAX_MAXCHAR(maxchar, ucs1lib_find_max_char(startptr, endptr));
     case PyUnicode_2BYTE_KIND:
-        return ucs2lib_find_max_char(startptr, endptr);
+        return MAX_MAXCHAR(maxchar, ucs2lib_find_max_char(startptr, endptr));
     case PyUnicode_4BYTE_KIND:
-        return ucs4lib_find_max_char(startptr, endptr);
+        return MAX_MAXCHAR(maxchar, ucs4lib_find_max_char(startptr, endptr));
     default:
         assert(0);
         return 0;
@@ -13740,7 +13744,7 @@
     Py_ssize_t pindex;
     Py_UCS4 signchar;
     Py_ssize_t buflen;
-    Py_UCS4 maxchar, bufmaxchar;
+    Py_UCS4 bufmaxchar;
     Py_ssize_t sublen;
     _PyUnicodeWriter *writer = &ctx->writer;
     Py_UCS4 fill;
@@ -13793,7 +13797,7 @@
         arg->width = len;
 
     /* Prepare the writer */
-    bufmaxchar = 127;
+    bufmaxchar = writer->maxchar;
     if (!(arg->flags & F_LJUST)) {
         if (arg->sign) {
             if ((arg->width-1) > len)
@@ -13804,8 +13808,7 @@
                 bufmaxchar = MAX_MAXCHAR(bufmaxchar, fill);
         }
     }
-    maxchar = _PyUnicode_FindMaxChar(str, 0, pindex+len);
-    bufmaxchar = MAX_MAXCHAR(bufmaxchar, maxchar);
+    bufmaxchar = _PyUnicode_FindMaxChar(str, 0, pindex+len, bufmaxchar);
     buflen = arg->width;
     if (arg->sign && len == arg->width)
         buflen++;
@@ -13976,7 +13979,8 @@
             }
             sublen = ctx.fmtpos - nonfmtpos;
             maxchar = _PyUnicode_FindMaxChar(ctx.fmtstr,
-                                             nonfmtpos, nonfmtpos + sublen);
+                                             nonfmtpos, nonfmtpos + sublen,
+                                             ctx.writer.maxchar);
             if (_PyUnicodeWriter_Prepare(&ctx.writer, sublen, maxchar) == -1)
                 goto onError;
 
diff -r 568019d6bf6b Python/formatter_unicode.c
--- a/Python/formatter_unicode.c	Sat Dec 22 14:57:16 2012 +0100
+++ b/Python/formatter_unicode.c	Sun Dec 23 18:19:57 2012 +0200
@@ -771,7 +771,7 @@
 
     calc_padding(len, format->width, format->align, &lpad, &rpad, &total);
 
-    maxchar = _PyUnicode_FindMaxChar(value, 0, len);
+    maxchar = _PyUnicode_FindMaxChar(value, 0, len, 127);
     if (lpad != 0 || rpad != 0)
         maxchar = Py_MAX(maxchar, format->fill_char);