diff --git a/include/uapi/linux/nfsd/nfsfh.h b/include/uapi/linux/nfsd/nfsfh.h
index ff0ca88b1c8f..427294dd56a1 100644
--- a/include/uapi/linux/nfsd/nfsfh.h
+++ b/include/uapi/linux/nfsd/nfsfh.h
@@ -64,13 +64,24 @@ struct nfs_fhbase_old {
  *   in include/linux/exportfs.h for currently registered values.
  */
 struct nfs_fhbase_new {
-	__u8		fb_version;	/* == 1, even => nfs_fhbase_old */
-	__u8		fb_auth_type;
-	__u8		fb_fsid_type;
-	__u8		fb_fileid_type;
-	__u32		fb_auth[1];
-/*	__u32		fb_fsid[0]; floating */
-/*	__u32		fb_fileid[0]; floating */
+	union {
+		struct {
+			__u8		fb_version_aux;	/* == 1, even => nfs_fhbase_old */
+			__u8		fb_auth_type_aux;
+			__u8		fb_fsid_type_aux;
+			__u8		fb_fileid_type_aux;
+			__u32		fb_auth[1];
+			/*	__u32		fb_fsid[0]; floating */
+			/*	__u32		fb_fileid[0]; floating */
+		};
+		struct {
+			__u8		fb_version;	/* == 1, even => nfs_fhbase_old */
+			__u8		fb_auth_type;
+			__u8		fb_fsid_type;
+			__u8		fb_fileid_type;
+			__u32		fb_auth_flex[]; /* flexible-array member */
+		};
+	};
 };
 
 struct knfsd_fh {
@@ -97,7 +108,7 @@ struct knfsd_fh {
 #define	fh_fsid_type		fh_base.fh_new.fb_fsid_type
 #define	fh_auth_type		fh_base.fh_new.fb_auth_type
 #define	fh_fileid_type		fh_base.fh_new.fb_fileid_type
-#define	fh_fsid			fh_base.fh_new.fb_auth
+#define	fh_fsid			fh_base.fh_new.fb_auth_flex
 
 /* Do not use, provided for userspace compatiblity. */
 #define	fh_auth			fh_base.fh_new.fb_auth