diff --git a/src/Extension.ts b/src/Extension.ts
index e54d51e..379655b 100644
--- a/src/Extension.ts
+++ b/src/Extension.ts
@@ -51,6 +51,10 @@ export function deactivate() {
 }
 
 function _handleContextChange(editor: vsc.TextEditor): void {
+    if (!editor || !editor.document) {
+        return;
+    }
+    
     switch (editor.document.languageId) {
         case 'xquery':
             XQueryLintingFeatureProvider.provideXQueryDiagnostics(editor);