diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index 4afa64c81304..0027beca5cd5 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -733,15 +733,18 @@ struct nft_set_ext_tmpl {
 /**
  *	struct nft_set_ext - set extensions
  *
- *	@genmask: generation mask
+ *	@genmask: generation mask, but also flags (see NFT_SET_ELEM_DEAD_BIT)
  *	@offset: offsets of individual extension types
  *	@data: beginning of extension data
+ *
+ *	This structure must be aligned to word size, otherwise atomic bitops
+ *	on genmask field can cause alignment failure on some archs.
  */
 struct nft_set_ext {
 	u8	genmask;
 	u8	offset[NFT_SET_EXT_NUM];
 	char	data[];
-};
+} __aligned(BITS_PER_LONG / 8);
 
 static inline void nft_set_ext_prepare(struct nft_set_ext_tmpl *tmpl)
 {