diff --git a/application/libraries/Api.php b/application/libraries/Api.php
index eebbb827..cc9484f4 100644
--- a/application/libraries/Api.php
+++ b/application/libraries/Api.php
@@ -216,15 +216,16 @@ class Api {
         {
             $api_field = substr($sort_token, 1);
 
-            $db_field = $this->model->db_field($api_field);
-
             $direction_operator = substr($sort_token, 0, 1);
 
             if ( ! in_array($direction_operator, ['-', '+']))
             {
-                throw new InvalidArgumentException('Invalid sort direction operator provided (expected "-" or "+"): ' . $direction_operator);
+                $direction_operator = '+';
+                $api_field = $sort_token;
             }
 
+            $db_field = $this->model->db_field($api_field);
+
             $direction = $direction_operator === '-' ? 'DESC' : 'ASC';
 
             $order_by[] = $db_field . ' ' . $direction;