diff -r c1ca1c4c131b Lib/ctypes/__init__.py
--- a/Lib/ctypes/__init__.py	Wed Aug 06 17:50:39 2014 +0300
+++ b/Lib/ctypes/__init__.py	Thu Aug 07 12:37:02 2014 +0300
@@ -49,7 +49,7 @@
     create_string_buffer(anInteger) -> character array
     create_string_buffer(aString, anInteger) -> character array
     """
-    if isinstance(init, (str, bytes)):
+    if isinstance(init, bytes):
         if size is None:
             size = len(init)+1
         buftype = c_char * size
@@ -284,7 +284,7 @@
     create_unicode_buffer(anInteger) -> character array
     create_unicode_buffer(aString, anInteger) -> character array
     """
-    if isinstance(init, (str, bytes)):
+    if isinstance(init, str):
         if size is None:
             size = len(init)+1
         buftype = c_wchar * size
diff -r c1ca1c4c131b Lib/ctypes/test/test_buffers.py
--- a/Lib/ctypes/test/test_buffers.py	Wed Aug 06 17:50:39 2014 +0300
+++ b/Lib/ctypes/test/test_buffers.py	Thu Aug 07 12:37:02 2014 +0300
@@ -21,6 +21,8 @@
         self.assertEqual(b[::2], b"ac")
         self.assertEqual(b[::5], b"a")
 
+        self.assertRaises(TypeError, create_string_buffer, "abc")
+
     def test_buffer_interface(self):
         self.assertEqual(len(bytearray(create_string_buffer(0))), 0)
         self.assertEqual(len(bytearray(create_string_buffer(1))), 1)
@@ -43,6 +45,8 @@
         self.assertEqual(b[::2], "ac")
         self.assertEqual(b[::5], "a")
 
+        self.assertRaises(TypeError, create_unicode_buffer, b"abc")
+
     @need_symbol('c_wchar')
     def test_unicode_conversion(self):
         b = create_unicode_buffer("abc")
diff -r c1ca1c4c131b Modules/_ctypes/_ctypes.c
--- a/Modules/_ctypes/_ctypes.c	Wed Aug 06 17:50:39 2014 +0300
+++ b/Modules/_ctypes/_ctypes.c	Thu Aug 07 12:37:02 2014 +0300
@@ -1471,7 +1471,7 @@
         Py_INCREF(Py_None);
         return Py_None;
     }
-    if (PyUnicode_Check(value) || PyBytes_Check(value)) {
+    if (PyUnicode_Check(value)) {
         PyCArgObject *parg;
         struct fielddesc *fd = _ctypes_get_fielddesc("Z");
 
@@ -1623,7 +1623,7 @@
         return (PyObject *)parg;
     }
     /* XXX struni: remove later */
-/* string */
+/* bytes */
     if (PyBytes_Check(value)) {
         PyCArgObject *parg;
         struct fielddesc *fd = _ctypes_get_fielddesc("z");
@@ -1640,23 +1640,6 @@
         }
         return (PyObject *)parg;
     }
-/* bytes */
-    if (PyByteArray_Check(value)) {
-        PyCArgObject *parg;
-        struct fielddesc *fd = _ctypes_get_fielddesc("z");
-
-        parg = PyCArgObject_new();
-        if (parg == NULL)
-            return NULL;
-        parg->pffi_type = &ffi_type_pointer;
-        parg->tag = 'z';
-        parg->obj = fd->setfunc(&parg->value, value, 0);
-        if (parg->obj == NULL) {
-            Py_DECREF(parg);
-            return NULL;
-        }
-        return (PyObject *)parg;
-    }
 /* unicode */
     if (PyUnicode_Check(value)) {
         PyCArgObject *parg;