diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index 1d826b6..999346f 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -374,7 +374,7 @@
         self.assertEqual(b1 + "def", bytes("abcdef"))
         self.assertEqual("def" + b1, bytes("defabc"))
         self.assertRaises(TypeError, lambda: b1 + u"def")
-        ##self.assertRaises(TypeError, lambda: u"abc" + b2)  # XXX FIXME
+        self.assertRaises(TypeError, lambda: u"abc" + b2)
 
     def test_repeat(self):
         b = bytes("abc")
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 4fe4d10..ce28692 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -5535,6 +5535,9 @@
 {
     PyUnicodeObject *u = NULL, *v = NULL, *w;
 
+    if (PyBytes_Check(left) || PyBytes_Check(right))
+        return PyBytes_Concat(left, right);
+
     /* Coerce the two arguments */
     u = (PyUnicodeObject *)PyUnicode_FromObject(left);
     if (u == NULL)