diff --git a/include/uapi/linux/in.h b/include/uapi/linux/in.h
index 14168225cecd..578daa6f816b 100644
--- a/include/uapi/linux/in.h
+++ b/include/uapi/linux/in.h
@@ -188,21 +188,13 @@ struct ip_mreq_source {
 };
 
 struct ip_msfilter {
+	__be32		imsf_multiaddr;
+	__be32		imsf_interface;
+	__u32		imsf_fmode;
+	__u32		imsf_numsrc;
 	union {
-		struct {
-			__be32		imsf_multiaddr_aux;
-			__be32		imsf_interface_aux;
-			__u32		imsf_fmode_aux;
-			__u32		imsf_numsrc_aux;
-			__be32		imsf_slist[1];
-		};
-		struct {
-			__be32		imsf_multiaddr;
-			__be32		imsf_interface;
-			__u32		imsf_fmode;
-			__u32		imsf_numsrc;
-			__be32		imsf_slist_flex[];
-		};
+		__be32		imsf_slist[1];
+		__DECLARE_FLEX_ARRAY(__be32, imsf_slist_flex);
 	};
 };