diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 683885b18ceba9bb56ca4cadebf87d01b7feb846..a39a542d8be5642760ac5b6d6b7bddc34cb9fea4 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3574,6 +3574,8 @@ nfsd4_open_downgrade(struct svc_rqst *rqstp,
 	if (!access_valid(od->od_share_access, cstate->minorversion)
 			|| !deny_valid(od->od_share_deny))
 		return nfserr_inval;
+	/* We don't yet support WANT bits: */
+	od->od_share_access &= NFS4_SHARE_ACCESS_MASK;
 
 	nfs4_lock_state();
 	status = nfs4_preprocess_confirmed_seqid_op(cstate, od->od_seqid,