diff --git a/src/Form/UiSelect.php b/src/Form/UiSelect.php
index 4d6bc31..7eca440 100644
--- a/src/Form/UiSelect.php
+++ b/src/Form/UiSelect.php
@@ -51,11 +51,11 @@ class UiSelect extends UiElement implements Extension {
                 $obj->text($key);
 
                 foreach($item as $subKey => $subItem) {
-                    $obj->append($this->createOption($subItem, $subKey, $isSelected));
+                    $obj->append($this->createOption((string) $subItem, $subKey, $isSelected));
                 }
             }
             else {
-                $obj = $this->createOption($item, $key, $isSelected);
+                $obj = $this->createOption((string) $item, $key, $isSelected);
             }
             
             $this->append($obj);