diff --git a/ghost/admin/controllers/post-settings-menu.js b/ghost/admin/controllers/post-settings-menu.js
index 2c47490bf6..b20c5442af 100644
--- a/ghost/admin/controllers/post-settings-menu.js
+++ b/ghost/admin/controllers/post-settings-menu.js
@@ -148,7 +148,7 @@ var PostSettingsMenuController = Ember.ObjectController.extend({
 
             newSlug = newSlug || slug;
 
-            newSlug = newSlug.trim();
+            newSlug = newSlug && newSlug.trim();
 
             // Ignore unchanged slugs or candidate slugs that are empty
             if (!newSlug || slug === newSlug) {