diff --git a/ipv4.c b/ipv4.c
index 56d83ac..c052d03 100644
--- a/ipv4.c
+++ b/ipv4.c
@@ -131,7 +131,7 @@
   } else if (nxthdr == IPPROTO_UDP) {
     iov_len =
       udp_packet(out, pos + 2, (const struct udphdr *)next_header, old_sum, new_sum, len_left);
-  } else if (nxthdr == IPPROTO_GRE) {
+  } else if (nxthdr == IPPROTO_GRE || nxthdr == IPPROTO_ESP) {
     iov_len = generic_packet(out, pos + 2, next_header, len_left);
   } else {
 #if CLAT_DEBUG