diff --git a/lib/src/default_extension_map.dart b/lib/src/default_extension_map.dart
index e66733f..a36818c 100644
--- a/lib/src/default_extension_map.dart
+++ b/lib/src/default_extension_map.dart
@@ -451,6 +451,7 @@ const Map<String, String> defaultExtensionMap = <String, String>{
   'mime': 'message/rfc822',
   'mj2': 'video/mj2',
   'mjp2': 'video/mj2',
+  'mjs': 'application/javascript',
   'mk3d': 'video/x-matroska',
   'mka': 'audio/x-matroska',
   'mks': 'video/x-matroska',
diff --git a/test/mime_type_test.dart b/test/mime_type_test.dart
index e99214a..a48627f 100644
--- a/test/mime_type_test.dart
+++ b/test/mime_type_test.dart
@@ -36,6 +36,7 @@ void main() {
       _expectMimeType('file.c', 'text/x-c');
       _expectMimeType('file.css', 'text/css');
       _expectMimeType('file.js', 'application/javascript');
+      _expectMimeType('file.mjs', 'application/javascript');
       _expectMimeType('file.ps', 'application/postscript');
       _expectMimeType('file.pdf', 'application/pdf');
       _expectMimeType('file.tiff', 'image/tiff');