diff --git a/net/l2tpv3.c b/net/l2tpv3.c
index 8e68e540ec..21d6119ed4 100644
--- a/net/l2tpv3.c
+++ b/net/l2tpv3.c
@@ -325,7 +325,7 @@ static int l2tpv3_verify_header(NetL2TPV3State *s, uint8_t *buf)
         if (s->cookie_is_64) {
             cookie = ldq_be_p(buf + s->cookie_offset);
         } else {
-            cookie = ldl_be_p(buf + s->cookie_offset);
+            cookie = ldl_be_p(buf + s->cookie_offset) & 0xffffffffULL;
         }
         if (cookie != s->rx_cookie) {
             if (!s->header_mismatch) {