diff -r 815b88454e3e Modules/_io/stringio.c
--- a/Modules/_io/stringio.c	Fri Aug 31 17:14:31 2012 -0400
+++ b/Modules/_io/stringio.c	Sun Sep 02 11:02:28 2012 +0100
@@ -764,6 +764,8 @@
 stringio_seekable(stringio *self, PyObject *args)
 {
     CHECK_INITIALIZED(self);
+    if (self->closed)
+       Py_RETURN_FALSE;
     Py_RETURN_TRUE;
 }
 
@@ -771,6 +773,8 @@
 stringio_readable(stringio *self, PyObject *args)
 {
     CHECK_INITIALIZED(self);
+    if (self->closed)
+       Py_RETURN_FALSE;
     Py_RETURN_TRUE;
 }
 
@@ -778,6 +782,8 @@
 stringio_writable(stringio *self, PyObject *args)
 {
     CHECK_INITIALIZED(self);
+    if (self->closed)
+       Py_RETURN_FALSE;
     Py_RETURN_TRUE;
 }