diff --git a/code/Control/UserDefinedFormAdmin.php b/code/Control/UserDefinedFormAdmin.php
index 69241d3f..e44e0430 100644
--- a/code/Control/UserDefinedFormAdmin.php
+++ b/code/Control/UserDefinedFormAdmin.php
@@ -308,7 +308,7 @@ private static function updateFormSubmissionFolderPermissions()
      * @return Folder
      * @throws ValidationException
      */
-    public static function getFormSubmissionFolder(string $subFolder = null): ?Folder
+    public static function getFormSubmissionFolder(?string $subFolder = null): ?Folder
     {
         $folderPath = static::config()->get('form_submissions_folder');
         if ($subFolder) {
diff --git a/code/Control/UserDefinedFormController.php b/code/Control/UserDefinedFormController.php
index 0044482c..5c3a96b2 100644
--- a/code/Control/UserDefinedFormController.php
+++ b/code/Control/UserDefinedFormController.php
@@ -134,7 +134,7 @@ protected function addUserFormsValidatei18n()
      *
      * @return array
      */
-    public function index(HTTPRequest $request = null)
+    public function index(?HTTPRequest $request = null)
     {
         $form = $this->Form();
         if ($this->Content && $form && !$this->config()->disable_form_content_shortcode) {
diff --git a/code/Model/EditableFormField/EditableFileField.php b/code/Model/EditableFormField/EditableFileField.php
index 71152988..da2ffd88 100755
--- a/code/Model/EditableFormField/EditableFileField.php
+++ b/code/Model/EditableFormField/EditableFileField.php
@@ -62,7 +62,7 @@ class EditableFileField extends EditableFormField
      * @param Folder|null $folder
      * @return string
      */
-    public static function getFolderPermissionString(Folder $folder = null)
+    public static function getFolderPermissionString(?Folder $folder = null)
     {
         $folderPermissions = static::getFolderPermissionTuple($folder);
 
@@ -84,7 +84,7 @@ public static function getFolderPermissionString(Folder $folder = null)
      * @param Folder|null $folder
      * @return array
      */
-    private static function getFolderPermissionTuple(Folder $folder = null)
+    private static function getFolderPermissionTuple(?Folder $folder = null)
     {
         $viewersOptionsField = [
             InheritedPermissions::INHERIT => _t(__CLASS__.'.INHERIT', 'Visibility for this folder is inherited from the parent folder'),
diff --git a/code/Task/RecoverUploadLocationsHelper.php b/code/Task/RecoverUploadLocationsHelper.php
index 75764f81..49fc2aaa 100644
--- a/code/Task/RecoverUploadLocationsHelper.php
+++ b/code/Task/RecoverUploadLocationsHelper.php
@@ -313,7 +313,7 @@ protected function recover($fileId, $expectedFolderId)
      *
      * @return int Number of files recovered
      */
-    protected function checkResidual($fileId, File $file, File $draft = null)
+    protected function checkResidual($fileId, File $file, ?File $draft = null)
     {
         if (!$this->filesVersioned) {
             return 0;