diff -r 020ebe0be33e Modules/mmapmodule.c
--- a/Modules/mmapmodule.c	Sat Apr 23 17:56:06 2011 +0200
+++ b/Modules/mmapmodule.c	Sun Apr 24 10:33:14 2011 -0300
@@ -642,9 +642,9 @@
         return NULL;
     } else {
         /* bounds check the values */
-        if (cnt < 0 || (cnt + dest) < cnt || (cnt + src) < cnt ||
-           src < 0 || src > self->size || (src + cnt) > self->size ||
-           dest < 0 || dest > self->size || (dest + cnt) > self->size) {
+        if ((PY_SIZE_MAX - dest) < cnt || (PY_SIZE_MAX - src) < cnt ||
+           src > self->size || (src + cnt) > self->size ||
+           dest > self->size || (dest + cnt) > self->size) {
             PyErr_SetString(PyExc_ValueError,
                 "source, destination, or count out of range");
             return NULL;