diff --git a/include/net/l3mdev.h b/include/net/l3mdev.h
index 5567d46..c43a9c7 100644
--- a/include/net/l3mdev.h
+++ b/include/net/l3mdev.h
@@ -39,7 +39,7 @@
 
 #ifdef CONFIG_NET_L3_MASTER_DEV
 
-int l3mdev_master_ifindex_rcu(struct net_device *dev);
+int l3mdev_master_ifindex_rcu(const struct net_device *dev);
 static inline int l3mdev_master_ifindex(struct net_device *dev)
 {
 	int ifindex;
@@ -179,7 +179,7 @@
 
 #else
 
-static inline int l3mdev_master_ifindex_rcu(struct net_device *dev)
+static inline int l3mdev_master_ifindex_rcu(const struct net_device *dev)
 {
 	return 0;
 }