diff --git a/encap-forward/Makefile b/encap-forward/Makefile
index d8f799b..898dfa8 100644
--- a/encap-forward/Makefile
+++ b/encap-forward/Makefile
@@ -3,6 +3,7 @@
 USER_TARGETS :=
 BPF_TARGETS := xdp_encap tc_bpf_encap
 EXTRA_DEPS := encap.h
+EXTRA_CFLAGS := $(if $(IPV6),-DIPV6)
 
 LIB_DIR = ../lib
 
diff --git a/encap-forward/encap.h b/encap-forward/encap.h
index 2c426b4..23d5daa 100644
--- a/encap-forward/encap.h
+++ b/encap-forward/encap.h
@@ -1,6 +1,6 @@
 #define NEXTHDR_IPV6		41
 
-
+#ifdef IPV6
 static void encap_ipv6(volatile void *data, volatile void *data_end)
 {
 	volatile struct ipv6hdr *ip6h;
@@ -27,6 +27,7 @@ static void encap_ipv6(volatile void *data, volatile void *data_end)
 	len = (data_end - data);
 	ip6h->payload_len = bpf_htons(len - sizeof(struct ethhdr) - sizeof(*ip6h));
 }
+#else
 
 static __always_inline __u16 csum_fold_helper(__u32 csum)
 {
@@ -60,3 +61,5 @@ static void encap_ipv4(volatile void *data, volatile void *data_end)
 	iph->tot_len = bpf_htons(len - sizeof(struct ethhdr));
 	iph->check = csum_fold_helper(bpf_csum_diff((__be32 *)iph, 0, (__be32 *)iph, sizeof(*iph), 0));
 }
+
+#endif
diff --git a/encap-forward/tc_bpf_encap.c b/encap-forward/tc_bpf_encap.c
index 9c87ba4..faaab5d 100644
--- a/encap-forward/tc_bpf_encap.c
+++ b/encap-forward/tc_bpf_encap.c
@@ -4,24 +4,34 @@
 #include <xdp/parsing_helpers.h>
 #include "encap.h"
 
+#ifdef IPV6
+#define OFFSET sizeof(struct ipv6hdr)
+#define ENCAP_TYPE BPF_F_ADJ_ROOM_ENCAP_L3_IPV6
+#else
+#define OFFSET sizeof(struct iphdr)
+#define ENCAP_TYPE BPF_F_ADJ_ROOM_ENCAP_L3_IPV4
+#endif
+
 SEC("classifier") int tc_encap(struct __sk_buff *skb)
 {
 	volatile void *data, *data_end;
+	size_t offset = OFFSET;
 	int ret = BPF_DROP;
-	size_t offset = sizeof(struct iphdr);
 
-
-	if (bpf_skb_adjust_room(skb, offset, BPF_ADJ_ROOM_MAC, BPF_F_ADJ_ROOM_ENCAP_L3_IPV4))
+	if (bpf_skb_adjust_room(skb, offset, BPF_ADJ_ROOM_MAC, ENCAP_TYPE))
 		goto out;
 
 	data = (void *)(long)skb->data;
 	data_end = (void *)(long)skb->data_end;
 
-//	encap_ipv6(ctx);
+#ifdef IPV6
+	encap_ipv6(data, data_end);
+#else
 	encap_ipv4(data, data_end);
 
 	/* proposed new helper for skipping source validation:
 	bpf_skb_set_source_valid(skb, 1); */
+#endif
 
 	ret = BPF_OK;
 out:
diff --git a/encap-forward/xdp_encap.c b/encap-forward/xdp_encap.c
index 8cd72fb..167a011 100644
--- a/encap-forward/xdp_encap.c
+++ b/encap-forward/xdp_encap.c
@@ -4,13 +4,18 @@
 #include <xdp/parsing_helpers.h>
 #include "encap.h"
 
+#ifdef IPV6
+#define OFFSET sizeof(struct ipv6hdr)
+#else
+#define OFFSET sizeof(struct iphdr)
+#endif
 
 SEC("prog") int xdp_encap(struct xdp_md *ctx)
 {
 	volatile struct ethhdr *ehdr, old_ehdr = {};
 	volatile void *data, *data_end;
+	size_t offset = OFFSET;
 	int ret = XDP_ABORTED;
-	size_t offset = sizeof(struct iphdr);
 
 	data = (void *)(long)ctx->data;
 	data_end = (void *)(long)ctx->data_end;
@@ -33,8 +38,11 @@ SEC("prog") int xdp_encap(struct xdp_md *ctx)
 	*ehdr = old_ehdr;
 	ehdr->h_proto = bpf_htons(ETH_P_IP);
 
-//	encap_ipv6(data, data_end);
+#ifdef IPV6
+	encap_ipv6(data, data_end);
+#else
 	encap_ipv4(data, data_end);
+#endif
 	ret = XDP_PASS;
 out:
 	return ret;
diff --git a/lib/common.mk b/lib/common.mk
index 1cd6e0d..b0fa130 100644
--- a/lib/common.mk
+++ b/lib/common.mk
@@ -36,8 +36,8 @@ endif
 # BPF-prog kern and userspace shares struct via header file:
 KERN_USER_H ?= $(wildcard common_kern_user.h)
 
-CFLAGS += -I$(HEADER_DIR) -I$(LIB_DIR)/util
-BPF_CFLAGS += -I$(HEADER_DIR)
+CFLAGS += -I$(HEADER_DIR) -I$(LIB_DIR)/util $(EXTRA_CFLAGS)
+BPF_CFLAGS += -I$(HEADER_DIR) $(EXTRA_CFLAGS)
 
 BPF_HEADERS := $(wildcard $(HEADER_DIR)/bpf/*.h) $(wildcard $(HEADER_DIR)/xdp/*.h)