diff --git a/dictionaries/filetypes.txt b/dictionaries/filetypes.txt
index d554f87eca3..d979372cabd 100644
--- a/dictionaries/filetypes.txt
+++ b/dictionaries/filetypes.txt
@@ -108,6 +108,7 @@ md
 mdoc
 mdown
 menu
+mjs
 mk
 mm
 mxml
diff --git a/src/LanguageIds.ts b/src/LanguageIds.ts
index 15094d90417..ce5e2aed658 100644
--- a/src/LanguageIds.ts
+++ b/src/LanguageIds.ts
@@ -55,7 +55,7 @@ export const languageExtensionDefinitions: LanguageExtensionDefinitions = [
     { id: 'jade', extensions: ['.jade', '.pug'], },
     { id: 'java', extensions: ['.java', '.jav'], },
     { id: 'javascriptreact', extensions: ['.jsx'], },
-    { id: 'javascript', extensions: ['.js', '.es6'], },
+    { id: 'javascript', extensions: ['.js', '.mjs', '.es6'], },
     { id: 'json', extensions: [
             '.json',
             '.bowerrc',