diff -r 919a3487fb00 Modules/_pickle.c
--- a/Modules/_pickle.c	Sat Sep 26 17:47:02 2015 -0700
+++ b/Modules/_pickle.c	Sun Sep 27 09:29:47 2015 +0300
@@ -1193,13 +1193,7 @@ static Py_ssize_t
 {
     Py_ssize_t num_read;
 
-    if (self->next_read_idx > PY_SSIZE_T_MAX - n) {
-        PickleState *st = _Pickle_GetGlobalState();
-        PyErr_SetString(st->UnpicklingError,
-                        "read would overflow (invalid bytecode)");
-        return -1;
-    }
-    if (self->next_read_idx + n <= self->input_len) {
+    if ((size_t)self->next_read_idx + (size_t)n <= (size_t)self->input_len) {
         *s = self->input_buffer + self->next_read_idx;
         self->next_read_idx += n;
         return n;