diff --git a/package.json b/package.json
index 24ad42e..9c9feea 100644
--- a/package.json
+++ b/package.json
@@ -114,6 +114,7 @@
 	},
 	"activationEvents": [
 		"onLanguage:xml",
+        "onLanguage:xsl",
         "onLanguage:xquery",
         "onCommand:xmlTools.minifyXml",
         "onCommand:xmlTools.evaluateXPath",
diff --git a/src/Extension.ts b/src/Extension.ts
index 9d4c562..fd23a79 100644
--- a/src/Extension.ts
+++ b/src/Extension.ts
@@ -11,6 +11,7 @@ export var GlobalState: vsc.Memento;
 export var WorkspaceState: vsc.Memento;
 
 const LANG_XML: string = 'xml';
+const LANG_XSL: string = 'xsl';
 const LANG_XQUERY: string = 'xquery;'
 const MEM_QUERY_HISTORY: string = 'xpathQueryHistory';
 
@@ -30,8 +31,8 @@ export function activate(ctx: vsc.ExtensionContext) {
 	
 	// register language feature providers
     ctx.subscriptions.push(
-        vsc.languages.registerDocumentFormattingEditProvider(LANG_XML, new XmlFormattingEditProvider()),
-        vsc.languages.registerDocumentRangeFormattingEditProvider(LANG_XML, new XmlFormattingEditProvider()),
+        vsc.languages.registerDocumentFormattingEditProvider([LANG_XML, LANG_XSL], new XmlFormattingEditProvider()),
+        vsc.languages.registerDocumentRangeFormattingEditProvider([LANG_XML, LANG_XSL], new XmlFormattingEditProvider()),
         
         vsc.languages.registerCompletionItemProvider(LANG_XQUERY, new XQueryCompletionItemProvider(), ':', '$')
     );