diff --git a/application/forms/Config/UserGroup/UserGroupBackendForm.php b/application/forms/Config/UserGroup/UserGroupBackendForm.php
index e8439ccaf..cfd615e47 100644
--- a/application/forms/Config/UserGroup/UserGroupBackendForm.php
+++ b/application/forms/Config/UserGroup/UserGroupBackendForm.php
@@ -123,7 +123,14 @@ class UserGroupBackendForm extends ConfigForm
             unset($data['name']);
         }
 
-        $this->config->setSection($name, $backendConfig->merge($data));
+        $backendConfig->merge($data);
+        foreach ($backendConfig->toArray() as $k => $v) {
+            if ($v === null) {
+                unset($backendConfig->$k);
+            }
+        }
+
+        $this->config->setSection($name, $backendConfig);
         return $this;
     }