diff --git a/snippets/copyright/index.js b/snippets/copyright/index.js
index fecd968..eecbf9c 100644
--- a/snippets/copyright/index.js
+++ b/snippets/copyright/index.js
@@ -86,7 +86,7 @@ async function fix_all_copy (folder, license = '', software = '') {
   await map_all_files (folder, (data, filename) => {
     const shebang = /^#!.*?\n\n/gu;
     const shebang_line = shebang.exec (data);
-    if (!(/\.js$/u).test (filename) && !regex.test (data))
+    if (!(/\.(?:js|ts|mjs)$/u).test (filename) && !regex.test (data))
       return null;
     return (shebang_line ? shebang_line[0] : '')
      + get_copyright_notice (license, software)