diff --git a/customfield/classes/category.php b/customfield/classes/category.php
index 0a7dff99851..4f37247cb9e 100644
--- a/customfield/classes/category.php
+++ b/customfield/classes/category.php
@@ -14,24 +14,14 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
-/**
- * Customfield category persistent class
- *
- * @package   core_customfield
- * @copyright 2018 Toni Barbera <toni@moodle.com>
- * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
- */
-
 namespace core_customfield;
 
 use core\persistent;
 
-defined('MOODLE_INTERNAL') || die;
-
 /**
- * Class category
+ * Customfield category persistent class
  *
- * @package core_customfield
+ * @package   core_customfield
  * @copyright 2018 Toni Barbera <toni@moodle.com>
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
@@ -60,7 +50,8 @@ class category extends persistent {
                 'descriptionformat' => [
                         'type' => PARAM_INT,
                         'default' => FORMAT_MOODLE,
-                        'optional' => true
+                        'optional' => true,
+                        'null' => NULL_ALLOWED,
                 ],
                 'component' => [
                         'type' => PARAM_COMPONENT
@@ -80,7 +71,8 @@ class category extends persistent {
                 'sortorder' => [
                         'type' => PARAM_INT,
                         'optional' => true,
-                        'default' => -1
+                        'default' => -1,
+                        'null' => NULL_ALLOWED,
                 ],
         );
     }
diff --git a/customfield/classes/field.php b/customfield/classes/field.php
index 7ba3ffced34..d763ee8b869 100644
--- a/customfield/classes/field.php
+++ b/customfield/classes/field.php
@@ -14,24 +14,14 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
-/**
- * Field persistent class
- *
- * @package   core_customfield
- * @copyright 2018 Toni Barbera <toni@moodle.com>
- * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
- */
-
 namespace core_customfield;
 
 use core\persistent;
 
-defined('MOODLE_INTERNAL') || die;
-
 /**
- * Class field
+ * Customfield field persistent class
  *
- * @package core_customfield
+ * @package   core_customfield
  * @copyright 2018 Toni Barbera <toni@moodle.com>
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
@@ -67,12 +57,14 @@ class field extends persistent {
                 'descriptionformat' => [
                         'type' => PARAM_INT,
                         'default' => FORMAT_MOODLE,
-                        'optional' => true
+                        'optional' => true,
+                        'null' => NULL_ALLOWED,
                 ],
                 'sortorder' => [
                         'type' => PARAM_INT,
                         'optional' => true,
                         'default' => -1,
+                        'null' => NULL_ALLOWED,
                 ],
                 'categoryid' => [
                         'type' => PARAM_INT
diff --git a/customfield/tests/category_controller_test.php b/customfield/tests/category_controller_test.php
index 7da1bdf817d..13397e17a06 100644
--- a/customfield/tests/category_controller_test.php
+++ b/customfield/tests/category_controller_test.php
@@ -61,6 +61,29 @@ final class category_controller_test extends \advanced_testcase {
         $this->assertTrue($c instanceof category_controller);
     }
 
+    /**
+     * Test creation of category instance from pre-defined object
+     */
+    public function test_constructor_from_record(): void {
+        $this->resetAfterTest();
+
+        // Create field object that matches the persistent/schema definition.
+        $category = category_controller::create(0, (object) [
+            'name' => 'Test',
+            'description' => null,
+            'descriptionformat' => null,
+            'component' => 'core_course',
+            'area' => 'course',
+            'itemid' => 0,
+            'sortorder' => null,
+        ]);
+
+        // Saving the category will validate the persistent internally.
+        $category->save();
+
+        $this->assertInstanceOf(category_controller::class, $category);
+    }
+
     /**
      * Test for function \core_customfield\field_controller::create() in case of wrong parameters
      */
diff --git a/customfield/tests/field_controller_test.php b/customfield/tests/field_controller_test.php
index f95253bad66..ee51af79d42 100644
--- a/customfield/tests/field_controller_test.php
+++ b/customfield/tests/field_controller_test.php
@@ -93,6 +93,30 @@ final class field_controller_test extends \advanced_testcase {
         );
     }
 
+    /**
+     * Test creation of field instance from pre-defined object
+     */
+    public function test_constructor_from_record(): void {
+        $this->resetAfterTest();
+
+        // Create field object that matches the persistent/schema definition.
+        $category = $this->get_generator()->create_category();
+        $field = field_controller::create(0, (object) [
+            'name' => 'Test',
+            'shortname' => 'test',
+            'type' => 'text',
+            'description' => null,
+            'descriptionformat' => null,
+            'sortorder' => null,
+            'configdata' => null,
+        ], $category);
+
+        // Saving the field will validate the persistent internally.
+        $field->save();
+
+        $this->assertInstanceOf(\customfield_text\field_controller::class, $field);
+    }
+
     /**
      * Test for function \core_customfield\field_controller::create() in case of wrong parameters
      */