diff --git a/net/phonet/pn_dev.c b/net/phonet/pn_dev.c
index 3287f8f..d5ad794 100644
--- a/net/phonet/pn_dev.c
+++ b/net/phonet/pn_dev.c
@@ -43,7 +43,7 @@
 	struct phonet_routes routes;
 };
 
-int phonet_net_id;
+int phonet_net_id __read_mostly;
 
 struct phonet_device_list *phonet_device_list(struct net *net)
 {