diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index 2bbf5163c0e2..63ff6b4d5d21 100644
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -1181,6 +1181,16 @@ int nf_nat_register_fn(struct net *net, u8 pf, const struct nf_hook_ops *ops,
 	struct nf_hook_ops *nat_ops;
 	int i, ret;
 
+#ifndef MODULE
+	/* If nf_nat_core is built-in and nf_nat_init() fails, dependent
+	 * modules like nft_chain_nat.ko may still call this function.
+	 * However, nat_net would be invalid, likely pointing to some other
+	 * per-net structure.
+	 */
+	if (WARN_ON_ONCE(!nf_nat_hook))
+		return -EOPNOTSUPP;
+#endif
+
 	if (WARN_ON_ONCE(pf >= ARRAY_SIZE(nat_net->nat_proto_net)))
 		return -EINVAL;