diff -r 403565c0e5de Python/marshal.c
--- a/Python/marshal.c	Tue Jan 28 02:24:22 2014 +0100
+++ b/Python/marshal.c	Tue Jan 28 11:09:41 2014 +0100
@@ -235,6 +235,11 @@ w_ref(PyObject *v, char *flag, WFILE *p)
     if (Py_REFCNT(v) == 1)
         return 0;
 
+    /* Storing duplicated numbers has a low impact on output size, whereas it
+       has an impact cost in the serialization performance */
+    if (PyLong_CheckExact(v) || PyFloat_CheckExact(v))
+        return 0;
+
     id = PyLong_FromVoidPtr((void*)v);
     if (id == NULL)
         goto err;