diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index 2a08337..645ef9d 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -174,6 +174,28 @@
         a = {}
         a[0] = a
         self.assertEqual(ascii(a), '{0: {...}}')
+        # Advanced checks for unicode strings
+        def _check_uni(s):
+            self.assertEqual(ascii(s), repr(s))
+        _check_uni("'")
+        _check_uni('"')
+        _check_uni('"\'')
+        _check_uni('\0')
+        _check_uni('\r\n\t .')
+        # Unprintable non-ASCII characters
+        _check_uni('\x85')
+        _check_uni('\u1fff')
+        _check_uni('\U00012fff')
+        # Lone surrogates
+        _check_uni('\ud800')
+        _check_uni('\udfff')
+        # Issue #9804: surrogates should be joined even for printable
+        # wide characters (UCS-2 builds).
+        self.assertEqual(ascii('\U0001d121'), "'\\U0001d121'")
+        # All together
+        s = "'\0\"\n\r\t abcd\x85é\U00012fff\uD800\U0001D121xxx."
+        self.assertEqual(ascii(s),
+            r"""'\'\x00"\n\r\t abcd\x85\xe9\U00012fff\ud800\U0001d121xxx.'""")
 
     def test_neg(self):
         x = -sys.maxsize-1
diff --git a/Lib/test/test_codeccallbacks.py b/Lib/test/test_codeccallbacks.py
index 82782b5..6105fc0 100644
--- a/Lib/test/test_codeccallbacks.py
+++ b/Lib/test/test_codeccallbacks.py
@@ -577,17 +577,31 @@
                 UnicodeEncodeError("ascii", "\uffff", 0, 1, "ouch")),
             ("\\uffff", 1)
         )
-        if sys.maxunicode>0xffff:
-            self.assertEquals(
-                codecs.backslashreplace_errors(
-                    UnicodeEncodeError("ascii", "\U00010000", 0, 1, "ouch")),
-                ("\\U00010000", 1)
-            )
-            self.assertEquals(
-                codecs.backslashreplace_errors(
-                    UnicodeEncodeError("ascii", "\U0010ffff", 0, 1, "ouch")),
-                ("\\U0010ffff", 1)
-            )
+        # 1 on UCS-4 builds, 2 on UCS-2
+        len_wide = len("\U00010000")
+        self.assertEquals(
+            codecs.backslashreplace_errors(
+                UnicodeEncodeError("ascii", "\U00010000",
+                                   0, len_wide, "ouch")),
+            ("\\U00010000", len_wide)
+        )
+        self.assertEquals(
+            codecs.backslashreplace_errors(
+                UnicodeEncodeError("ascii", "\U0010ffff",
+                                   0, len_wide, "ouch")),
+            ("\\U0010ffff", len_wide)
+        )
+        # Lone surrogates (regardless of unicode width)
+        self.assertEquals(
+            codecs.backslashreplace_errors(
+                UnicodeEncodeError("ascii", "\ud800", 0, 1, "ouch")),
+            ("\\ud800", 1)
+        )
+        self.assertEquals(
+            codecs.backslashreplace_errors(
+                UnicodeEncodeError("ascii", "\udfff", 0, 1, "ouch")),
+            ("\\udfff", 1)
+        )
 
     def test_badhandlerresults(self):
         results = ( 42, "foo", (1,2,3), ("foo", 1, 3), ("foo", None), ("foo",), ("foo", 1, 3), ("foo", None), ("foo",) )