diff --git a/extension.js b/extension.js
index 931499f3..23d6708b 100644
--- a/extension.js
+++ b/extension.js
@@ -21,7 +21,7 @@ exports.activate = function activateStylelint(context) {
       }
     }
   }, {
-    documentSelector: ['css', 'sass'],
+    documentSelector: ['css', 'sass', 'less'],
     synchronize: {
       configurationSection: 'stylelint',
       fileEvents: vscode.workspace.createFileSystemWatcher('**/{.stylelintrc,stylelint.config.js}')
diff --git a/server.js b/server.js
index f60db2e6..3d28b83f 100644
--- a/server.js
+++ b/server.js
@@ -12,13 +12,18 @@ let configOverrides;
 const connection = langServer.createConnection(process.stdin, process.stdout);
 const documents = new langServer.TextDocuments();
 
+const syntaxConfig = {
+  '.scss': 'scss',
+  '.less': 'less'
+};
+
 function validate(document) {
   return stylelintVSCode({
     code: document.getText(),
     config,
     configOverrides,
     configBasedir,
-    syntax: path.extname(String(document.uri)).toLowerCase() === '.scss' ? 'scss' : null
+    syntax: syntaxConfig[path.extname(String(document.uri)).toLowerCase()]
   }).then(diagnostics => {
     connection.sendDiagnostics({uri: document.uri, diagnostics});
   }).catch(err => {