diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index 43d8c5d39ee..53c7800c9a3 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -392,6 +392,7 @@ class UnicodeTest(
 
         self.assertEqual(u'%c' % 0x1234, u'\u1234')
         self.assertRaises(OverflowError, u"%c".__mod__, (sys.maxunicode+1,))
+        self.assertRaises(ValueError, u"%.1\u1032f".__mod__, (1.0/3))
 
         for num in range(0x00,0x80):
             char = chr(num)
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index d05685514de..571f607c3c1 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -8607,7 +8607,7 @@ PyObject *PyUnicode_Format(PyObject *format,
                 else if (c >= '0' && c <= '9') {
                     prec = c - '0';
                     while (--fmtcnt >= 0) {
-                        c = Py_CHARMASK(*fmt++);
+                        c = *fmt++;
                         if (c < '0' || c > '9')
                             break;
                         if ((prec*10) / 10 != prec) {