diff --git a/include/net/tcp.h b/include/net/tcp.h
index c9766f8..4062b4f 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -730,6 +730,7 @@
 #define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))
 
 
+#if IS_ENABLED(CONFIG_IPV6)
 /* This is the variant of inet6_iif() that must be used by TCP,
  * as TCP moves IP6CB into a different location in skb->cb[]
  */
@@ -737,6 +738,7 @@
 {
 	return TCP_SKB_CB(skb)->header.h6.iif;
 }
+#endif
 
 /* Due to TSO, an SKB can be composed of multiple actual
  * packets.  To keep these tracked properly, we use this.