diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index f82ea12bac37..425b95eb7e87 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -322,8 +322,13 @@ int l2tp_session_register(struct l2tp_session *session,
 
 		spin_lock_bh(&pn->l2tp_session_hlist_lock);
 
+		/* IP encap expects session IDs to be globally unique, while
+		 * UDP encap doesn't.
+		 */
 		hlist_for_each_entry(session_walk, g_head, global_hlist)
-			if (session_walk->session_id == session->session_id) {
+			if (session_walk->session_id == session->session_id &&
+			    (session_walk->tunnel->encap == L2TP_ENCAPTYPE_IP ||
+			     tunnel->encap == L2TP_ENCAPTYPE_IP)) {
 				err = -EEXIST;
 				goto err_tlock_pnlock;
 			}