diff --git a/extensions/windowsNavigator/extension.js b/extensions/windowsNavigator/extension.js
index c38a98f1..50beaa85 100644
--- a/extensions/windowsNavigator/extension.js
+++ b/extensions/windowsNavigator/extension.js
@@ -253,6 +253,8 @@ function removeInjection(object, injection, name) {
 }
 
 function disable() {
+    let i;
+
     for (i in workspaceInjections)
         removeInjection(Workspace.Workspace.prototype, workspaceInjections, i);
     for (i in winInjections)