diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 60c6b073d65f..08387140a646 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -1154,7 +1154,6 @@ static inline void mptcp_pm_close_subflow(struct mptcp_sock *msk)
 	spin_unlock_bh(&msk->pm.lock);
 }
 
-void mptcp_sockopt_sync(struct mptcp_sock *msk, struct sock *ssk);
 void mptcp_sockopt_sync_locked(struct mptcp_sock *msk, struct sock *ssk);
 
 static inline struct mptcp_ext *mptcp_get_ext(const struct sk_buff *skb)