diff --git a/include/class.forms.php b/include/class.forms.php
index a09f25cdbd38ed5807b687b0f0e104e92e7a78dd..92876b2324c7a0645c2fa63c2ee4186fa049978e 100644
--- a/include/class.forms.php
+++ b/include/class.forms.php
@@ -284,7 +284,7 @@ class FormField {
      * $value - PHP value of the field's content
      */
     function toString($value) {
-        return $value;
+        return (string) $value;
     }
 
     /**