diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c
index 8407c11..ca5fa88 100644
--- a/Modules/mmapmodule.c
+++ b/Modules/mmapmodule.c
@@ -1373,7 +1373,7 @@
 						     dwDesiredAccess,
 						     off_hi,
 						     off_lo,
-						     0);
+						     m_obj->size);
 		if (m_obj->data != NULL)
 			return (PyObject *)m_obj;
 		else