diff --git a/thumb.go b/thumb.go
index fcb20e9..20a01d6 100644
--- a/thumb.go
+++ b/thumb.go
@@ -104,6 +104,7 @@ func (this *Server) handleThumbInternal(ctx context.Context, w http.ResponseWrit
 		return err
 	}
 
+	w.Header().Set(`Cache-Control`, `max-age=31536000, immutable`)
 	w.Header().Set(`Content-Length`, fmt.Sprintf("%d", len(thumb)))
 	w.Header().Set(`Content-Type`, `image/jpeg`)
 	w.WriteHeader(200)