-func (rp *remoteProxy) Get(ctx context.Context, w http.ResponseWriter, r *http.Request, cluster *arvados.Cluster) {
+func (rp *remoteProxy) Get(ctx context.Context, w http.ResponseWriter, r *http.Request, cluster *arvados.Cluster, volmgr *RRVolumeManager) {
+ // Intervening proxies must not return a cached GET response
+ // to a prior request if a X-Keep-Signature request header has
+ // been added or changed.
+ w.Header().Add("Vary", "X-Keep-Signature")
+