diff --git a/src/Forms/FormField.php b/src/Forms/FormField.php
index 632335391..5a9b65bef 100644
--- a/src/Forms/FormField.php
+++ b/src/Forms/FormField.php
@@ -1424,7 +1424,7 @@ class FormField extends RequestHandler
         $field = $classOrCopy;
 
         if (!is_object($field)) {
-            $field = new $classOrCopy($this->name);
+            $field = $classOrCopy::create($this->name);
         }
 
         $field
diff --git a/src/Forms/TreeDropdownField_Readonly.php b/src/Forms/TreeDropdownField_Readonly.php
index fed1a1765..c51867098 100644
--- a/src/Forms/TreeDropdownField_Readonly.php
+++ b/src/Forms/TreeDropdownField_Readonly.php
@@ -17,7 +17,7 @@ class TreeDropdownField_Readonly extends TreeDropdownField
         }
 
         $source = [ $this->value => $title ];
-        $field = new LookupField($this->name, $this->title, $source);
+        $field = LookupField::create($this->name, $this->title, $source);
         $field->setValue($this->value);
         $field->setForm($this->form);
         return $field->Field();