diff -r a70ca6f35327 Modules/_io/bufferedio.c
--- a/Modules/_io/bufferedio.c	Mon Mar 30 11:48:50 2015 -0400
+++ b/Modules/_io/bufferedio.c	Mon Mar 30 17:41:04 2015 -0400
@@ -882,6 +882,7 @@
     PyObject *res = NULL;
 
     CHECK_INITIALIZED(self)
+    CHECK_CLOSED(self, "peek of closed file")
     if (!PyArg_ParseTuple(args, "|n:peek", &n)) {
         return NULL;
     }