diff --git a/ipv6.c b/ipv6.c
index c9b547e..ca3e4c6 100644
--- a/ipv6.c
+++ b/ipv6.c
@@ -163,7 +163,7 @@
   } else if (protocol == IPPROTO_UDP) {
     iov_len =
       udp_packet(out, pos + 2, (const struct udphdr *)next_header, old_sum, new_sum, len_left);
-  } else if (protocol == IPPROTO_GRE) {
+  } else if (protocol == IPPROTO_GRE || protocol == IPPROTO_ESP) {
     iov_len = generic_packet(out, pos + 2, next_header, len_left);
   } else {
 #if CLAT_DEBUG