diff -r 4c2f3240ad65 Lib/posixpath.py
--- a/Lib/posixpath.py	Thu Jul 17 00:00:26 2014 +0300
+++ b/Lib/posixpath.py	Fri Jul 18 17:35:52 2014 +0300
@@ -83,12 +83,10 @@
             else:
                 path += sep + b
     except TypeError:
-        valid_types = all(isinstance(s, (str, bytes, bytearray))
-                          for s in (a, ) + p)
-        if valid_types:
+        if all(isinstance(s, (str, bytes)) for s in (a,) + p):
             # Must have a mixture of text and binary data
             raise TypeError("Can't mix strings and bytes in path "
-                            "components.") from None
+                            "components") from None
         raise
     return path
 
diff -r 4c2f3240ad65 Lib/test/test_posixpath.py
--- a/Lib/test/test_posixpath.py	Thu Jul 17 00:00:26 2014 +0300
+++ b/Lib/test/test_posixpath.py	Fri Jul 18 17:35:52 2014 +0300
@@ -57,21 +57,17 @@
         self.assertEqual(posixpath.join(b"/foo/", b"bar/", b"baz/"),
                          b"/foo/bar/baz/")
 
-        def check_error_msg(list_of_args, msg):
-            """Check posixpath.join raises friendly TypeErrors."""
-            for args in (item for perm in list_of_args
-                              for item in itertools.permutations(perm)):
-                with self.assertRaises(TypeError) as cm:
-                    posixpath.join(*args)
-                self.assertEqual(msg, cm.exception.args[0])
-
-        check_error_msg([[b'bytes', 'str'], [bytearray(b'bytes'), 'str']],
-                        "Can't mix strings and bytes in path components.")
+    def test_join_errors(self):
+        # Check posixpath.join raises friendly TypeErrors.
+        errmsg = "Can't mix strings and bytes in path components"
+        with self.assertRaisesRegex(TypeError, errmsg):
+            posixpath.join(b'bytes', 'str')
+        with self.assertRaisesRegex(TypeError, errmsg):
+            posixpath.join('str', b'bytes')
         # regression, see #15377
         with self.assertRaises(TypeError) as cm:
             posixpath.join(None, 'str')
-        self.assertNotEqual("Can't mix strings and bytes in path components.",
-                            cm.exception.args[0])
+        self.assertNotEqual(cm.exception.args[0], errmsg)
 
     def test_split(self):
         self.assertEqual(posixpath.split("/foo/bar"), ("/foo", "bar"))