1 files changed, 11 insertions, 4 deletions
diff --git a/cli/tools/fmt.rs b/cli/tools/fmt.rs
index a2d9a3027..547dc379b 100644
--- a/cli/tools/fmt.rs
+++ b/cli/tools/fmt.rs
@@ -49,7 +49,14 @@ pub async fn format(
   fmt_options: FmtOptions,
 ) -> Result<(), AnyError> {
   if fmt_options.is_stdin {
-    return format_stdin(fmt_options);
+    return format_stdin(
+      fmt_options,
+      cli_options
+        .ext_flag()
+        .as_ref()
+        .map(|s| s.as_str())
+        .unwrap_or("ts"),
+    );
   }
 
   let files = fmt_options.files;
@@ -456,14 +463,14 @@ fn format_ensure_stable(
 }
 
 /// Format stdin and write result to stdout.
-/// Treats input as TypeScript or as set by `--ext` flag.
+/// Treats input as set by `--ext` flag.
 /// Compatible with `--check` flag.
-fn format_stdin(fmt_options: FmtOptions) -> Result<(), AnyError> {
+fn format_stdin(fmt_options: FmtOptions, ext: &str) -> Result<(), AnyError> {
   let mut source = String::new();
   if stdin().read_to_string(&mut source).is_err() {
     bail!("Failed to read from stdin");
   }
-  let file_path = PathBuf::from(format!("_stdin.{}", fmt_options.ext));
+  let file_path = PathBuf::from(format!("_stdin.{ext}"));
   let formatted_text = format_file(&file_path, &source, &fmt_options.options)?;
   if fmt_options.check {
     if formatted_text.is_some() {