diff --git a/net/ipv4/netfilter/nf_nat_proto_gre.c b/net/ipv4/netfilter/nf_nat_proto_gre.c
index b887ebb..a1e4da1 100644
--- a/net/ipv4/netfilter/nf_nat_proto_gre.c
+++ b/net/ipv4/netfilter/nf_nat_proto_gre.c
@@ -104,7 +104,7 @@
 {
 	struct gre_hdr *greh;
 	struct gre_hdr_pptp *pgreh;
-	struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
+	const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
 	unsigned int hdroff = iphdroff + iph->ihl * 4;
 
 	/* pgreh includes two optional 32bit fields which are not required
diff --git a/net/netfilter/nf_conntrack_proto_gre.c b/net/netfilter/nf_conntrack_proto_gre.c
index 4a185f6..e10024a 100644
--- a/net/netfilter/nf_conntrack_proto_gre.c
+++ b/net/netfilter/nf_conntrack_proto_gre.c
@@ -161,9 +161,11 @@
 			   unsigned int dataoff,
 			   struct nf_conntrack_tuple *tuple)
 {
-	struct gre_hdr_pptp _pgrehdr, *pgrehdr;
+	const struct gre_hdr_pptp *pgrehdr;
+	struct gre_hdr_pptp _pgrehdr;
 	__be16 srckey;
-	struct gre_hdr _grehdr, *grehdr;
+	const struct gre_hdr *grehdr;
+	struct gre_hdr _grehdr;
 
 	/* first only delinearize old RFC1701 GRE header */
 	grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);