diff --git a/elisp/private/tools/gen-proto.el b/elisp/private/tools/gen-proto.el
index 04e7ee67e..7f7e28b1d 100644
--- a/elisp/private/tools/gen-proto.el
+++ b/elisp/private/tools/gen-proto.el
@@ -166,6 +166,7 @@ enumeration type, and VALUES is a list of (NAME NUMBER) pairs."
       (cons output-file
             (buffer-substring-no-properties (point-min) (point-max))))))
 
+(unless noninteractive (user-error "This file works only in batch mode"))
 (set-binary-mode 'stdin :binary)
 (set-binary-mode 'stdout :binary)
 (let* ((standard-output #'external-debugging-output)
diff --git a/tests/proto/integration/cat.el b/tests/proto/integration/cat.el
index 3b96f4678..5c16f4c3e 100644
--- a/tests/proto/integration/cat.el
+++ b/tests/proto/integration/cat.el
@@ -1,6 +1,6 @@
 ;;; cat.el --- helper binary for module test -*- lexical-binding: t; -*-
 
-;; Copyright 2024, 2025 Philipp Stephani
+;; Copyright 2024-2026 Philipp Stephani
 ;;
 ;; Licensed under the Apache License, Version 2.0 (the "License");
 ;; you may not use this file except in compliance with the License.
@@ -24,6 +24,7 @@
 
 (require 'elisp/proto/module)
 
+(unless noninteractive (user-error "This file works only in batch mode"))
 (set-binary-mode 'stdin :binary)
 (set-binary-mode 'stdout :binary)