diff --git a/src/openvpn/proto.c b/src/openvpn/proto.c
index 13fe0a54..785c021f 100644
--- a/src/openvpn/proto.c
+++ b/src/openvpn/proto.c
@@ -70,7 +70,7 @@ is_ipv_X(int tunnel_type, struct buffer *buf, int ip_ver)
         if (proto == htons(OPENVPN_ETH_P_8021Q))
         {
             const struct openvpn_8021qhdr *evh;
-            if (BLENZ(buf) < sizeof(struct openvpn_ethhdr) + sizeof(struct openvpn_iphdr))
+            if (BLENZ(buf) < sizeof(struct openvpn_8021qhdr) + sizeof(struct openvpn_iphdr))
             {
                 return false;
             }