diff --git a/include/class.dynamic_forms.php b/include/class.dynamic_forms.php
index c22e563fee5ad6f21a2d45e49374ed11f624913a..9705d54d4cd2666ff6e1084ef8e81e8a33a56291 100644
--- a/include/class.dynamic_forms.php
+++ b/include/class.dynamic_forms.php
@@ -906,7 +906,8 @@ class SelectionField extends FormField {
     }
 
     function toString($item) {
-        return ($item instanceof DynamicListItem) ? $item->toString() : $item;
+        return ($item instanceof DynamicListItem)
+            ? $item->toString() : (string) $item;
     }
 
     function validateEntry($item) {