diff --git a/openid_client_ax.module b/openid_client_ax.module
index 2ffdb81..97647f0 100644
--- a/openid_client_ax.module
+++ b/openid_client_ax.module
@@ -690,5 +690,13 @@ function openid_client_ax_schema_definitions() {
       'section'     => t('Extra-Information'),
     ),
   );
+
+  // Invokation of hook_openid_client_ax_schema() and
+  // hook_openid_client_ax_schema_alter() allowing other modules to inject
+  // their elements or modify the defined elements.
+  // @todo: static caching or Drupal DB cache might be needed
+  $attributes = array_merge($attributes, module_invoke_all('openid_client_ax_schema'));
+  drupal_alter('openid_client_ax_schema', $attributes);
+
   return $attributes;
 }