diff --git a/git_cl.py b/git_cl.py
index 143ff3b1d..08d6837d9 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -5797,7 +5797,7 @@ def CMDformat(parser, args):
   diff_files = [x for x in diff_files if os.path.isfile(x)]
 
   if opts.js:
-    CLANG_EXTS.append('.js')
+    CLANG_EXTS.extend(['.js', '.ts'])
 
   clang_diff_files = [x for x in diff_files if MatchingFileType(x, CLANG_EXTS)]
   python_diff_files = [x for x in diff_files if MatchingFileType(x, ['.py'])]