diff --git a/src/constants.ts b/src/constants.ts
index 6261aee..b64536a 100644
--- a/src/constants.ts
+++ b/src/constants.ts
@@ -17,6 +17,7 @@ export namespace diagnosticCollections {
 export namespace languageIds {
     export const xml = "xml";
     export const xsd = "xsd";
+    export const xsl = "xsl";
     export const xquery = "xquery";
 }
 
diff --git a/src/extension.ts b/src/extension.ts
index ee975af..ebcb2a0 100644
--- a/src/extension.ts
+++ b/src/extension.ts
@@ -17,7 +17,12 @@ import * as constants from "./constants";
 export function activate(context: ExtensionContext) {
     ExtensionState.configure(context);
 
-    const xmlXsdDocSelector = [...createDocumentSelector(constants.languageIds.xml), ...createDocumentSelector(constants.languageIds.xsd)];
+    const xmlXsdDocSelector = [
+        ...createDocumentSelector(constants.languageIds.xml),
+        ...createDocumentSelector(constants.languageIds.xsd),
+        ...createDocumentSelector(constants.languageIds.xsl)
+    ];
+
     const xqueryDocSelector = createDocumentSelector(constants.languageIds.xquery);
 
     /* Completion Features */