diff -r 1f27572a10ce Lib/test/test_builtin.py
--- a/Lib/test/test_builtin.py	Wed Aug 22 23:34:50 2012 -0700
+++ b/Lib/test/test_builtin.py	Sun Aug 26 20:48:12 2012 +1000
@@ -1086,6 +1086,12 @@
             sys.stdin = io.StringIO()
             self.assertRaises(EOFError, input)
 
+            sys.stdin = io.StringIO("the meaning of life")
+            sys.stdout = BitBucket()
+            sys.stdout.encoding = None
+            sys.stdout.errors = None
+            self.assertEqual(input('prompt'), "the meaning of life")
+
             del sys.stdout
             self.assertRaises(RuntimeError, input, 'prompt')
             del sys.stdin
diff -r 1f27572a10ce Python/bltinmodule.c
--- a/Python/bltinmodule.c	Wed Aug 22 23:34:50 2012 -0700
+++ b/Python/bltinmodule.c	Sun Aug 26 20:48:12 2012 +1000
@@ -1709,8 +1709,19 @@
                 goto _readline_errors;
             stdout_encoding_str = _PyUnicode_AsString(stdout_encoding);
             stdout_errors_str = _PyUnicode_AsString(stdout_errors);
-            if (!stdout_encoding_str || !stdout_errors_str)
-                goto _readline_errors;
+            if (!stdout_encoding_str || !stdout_errors_str) {
+                /* invalid encoding or errors attributes on stdin,
+                   check stderr for valid values */
+                PyErr_Clear();
+                stdout_encoding = _PyObject_GetAttrId(ferr, &PyId_encoding);
+                stdout_errors = _PyObject_GetAttrId(ferr, &PyId_errors);
+                if (!stdout_encoding || !stdout_errors)
+                    goto _readline_errors;
+                stdout_encoding_str = _PyUnicode_AsString(stdout_encoding);
+                stdout_errors_str = _PyUnicode_AsString(stdout_errors);
+                if (!stdout_encoding_str || !stdout_errors_str)
+                    goto _readline_errors;
+            }
             stringpo = PyObject_Str(promptarg);
             if (stringpo == NULL)
                 goto _readline_errors;