diff --git a/cmd/godoc/handlers.go b/cmd/godoc/handlers.go
index dda1bb87..600be685 100644
--- a/cmd/godoc/handlers.go
+++ b/cmd/godoc/handlers.go
@@ -54,6 +54,7 @@ func (h hostEnforcerHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		http.Redirect(w, r, r.URL.String(), http.StatusFound)
 		return
 	}
+	w.Header().Set("Strict-Transport-Security", "max-age=31536000; preload")
 	h.h.ServeHTTP(w, r)
 }