diff --git a/sys/contrib/pf/net/pf.c b/sys/contrib/pf/net/pf.c
index d29be54ed8d..99958c7eb74 100644
--- a/sys/contrib/pf/net/pf.c
+++ b/sys/contrib/pf/net/pf.c
@@ -6334,7 +6334,8 @@ pf_test6(int dir, struct ifnet *ifp, struct mbuf **m0)
 			goto done;
 		}
 		if (dir == PF_IN && pf_check_proto_cksum(m, off,
-		    ntohs(h->ip6_plen), IPPROTO_TCP, AF_INET6)) {
+		    ntohs(h->ip6_plen) - (off - sizeof(struct ip6_hdr)),
+		    IPPROTO_TCP, AF_INET6)) {
 			action = PF_DROP;
 			goto done;
 		}
@@ -6372,7 +6373,8 @@ pf_test6(int dir, struct ifnet *ifp, struct mbuf **m0)
 			goto done;
 		}
 		if (dir == PF_IN && uh.uh_sum && pf_check_proto_cksum(m,
-		    off, ntohs(h->ip6_plen), IPPROTO_UDP, AF_INET6)) {
+		    off, ntohs(h->ip6_plen) - (off - sizeof(struct ip6_hdr)),
+		    IPPROTO_UDP, AF_INET6)) {
 			action = PF_DROP;
 			goto done;
 		}
@@ -6411,7 +6413,8 @@ pf_test6(int dir, struct ifnet *ifp, struct mbuf **m0)
 			goto done;
 		}
 		if (dir == PF_IN && pf_check_proto_cksum(m, off,
-		    ntohs(h->ip6_plen), IPPROTO_ICMPV6, AF_INET6)) {
+		    ntohs(h->ip6_plen)  - (off - sizeof(struct ip6_hdr)),
+		    IPPROTO_ICMPV6, AF_INET6)) {
 			action = PF_DROP;
 			goto done;
 		}