diff --git a/.upgrade.yml b/.upgrade.yml
index d57c41765..a2fec5e91 100644
--- a/.upgrade.yml
+++ b/.upgrade.yml
@@ -1325,6 +1325,8 @@ warnings:
       replacement: 'writeJavascriptToBody'
     'SilverStripe\Forms\Formfield->dontEscape':
       message: 'FormField::$dontEscape has been removed. Escaping is now managed on a class by class basis.'
+    'SilverStripe\Security\LoginForm->authenticator_class':
+      message: 'authenticator_class is deprecated. Use getAuthenticatorClass/setAuthenticatorClass.'
     'SilverStripe\Security\Permission::$declared_permissions':
       message: 'Deprecated'
     'SilverStripe\Security\Permission::$declared_permissions_list':
@@ -1387,4 +1389,4 @@ warnings:
       url: 'https://docs.silverstripe.org/en/4/changelogs/4.4.0#resources-dir'
       replacement: 'RESOURCES_DIR'
 renameWarnings:
-  - Form
\ No newline at end of file
+  - Form
diff --git a/src/Security/LoginForm.php b/src/Security/LoginForm.php
index f1622f5e1..a927915a9 100644
--- a/src/Security/LoginForm.php
+++ b/src/Security/LoginForm.php
@@ -15,26 +15,56 @@ use SilverStripe\Forms\Form;
  */
 abstract class LoginForm extends Form
 {
-
     /**
-     * Authenticator class to use with this login form
-     *
-     * Set this variable to the authenticator class to use with this login
-     * form.
+     * @deprecated 4.4.0:5.0.0 Use getAuthenticatorClass() or setAuthenticatorClass() instead
      * @var string
      */
     protected $authenticator_class;
 
+    /**
+     * Authenticator class to use with this login form
+     *
+     * Set this variable to the authenticator class to use with this login form.
+     *
+     * @var string
+     */
+    protected $authenticatorClass;
+
+    /**
+     * Set the authenticator class name to use
+     *
+     * @param string $class
+     * @return $this
+     */
     public function setAuthenticatorClass($class)
     {
-        $this->authenticator_class = $class;
-        $authenticatorField = $this->Fields()->dataFieldByName('AuthenticationMethod');
+        $this->authenticatorClass = $class;
+
+        /** @var FieldList|null $fields */
+        $fields = $this->Fields();
+        if (!$fields) {
+            return $this;
+        }
+
+        $authenticatorField = $fields->dataFieldByName('AuthenticationMethod');
         if ($authenticatorField) {
             $authenticatorField->setValue($class);
         }
+
         return $this;
     }
 
+    /**
+     * Returns the authenticator class name to use
+     *
+     * @return string
+     */
+    public function getAuthenticatorClass()
+    {
+        // B/C for deprecated authenticator_class property
+        return $this->authenticator_class ?: $this->authenticatorClass;
+    }
+
     /**
      * Return the title of the form for use in the frontend
      * For tabs with multiple login methods, for example.
diff --git a/src/Security/MemberAuthenticator/CMSMemberLoginForm.php b/src/Security/MemberAuthenticator/CMSMemberLoginForm.php
index 636df9f1f..361677931 100644
--- a/src/Security/MemberAuthenticator/CMSMemberLoginForm.php
+++ b/src/Security/MemberAuthenticator/CMSMemberLoginForm.php
@@ -30,7 +30,7 @@ class CMSMemberLoginForm extends MemberLoginForm
     {
         $this->controller = $controller;
 
-        $this->authenticator_class = $authenticatorClass;
+        $this->setAuthenticatorClass($authenticatorClass);
 
         $fields = $this->getFormFields();
 
@@ -48,7 +48,7 @@ class CMSMemberLoginForm extends MemberLoginForm
     {
         // Set default fields
         $fields = FieldList::create([
-            HiddenField::create("AuthenticationMethod", null, $this->authenticator_class, $this),
+            HiddenField::create("AuthenticationMethod", null, $this->getAuthenticatorClass(), $this),
             HiddenField::create('tempid', null, $this->controller->getRequest()->requestVar('tempid')),
             PasswordField::create("Password", _t('SilverStripe\\Security\\Member.PASSWORD', 'Password'))
         ]);
diff --git a/src/Security/MemberAuthenticator/MemberLoginForm.php b/src/Security/MemberAuthenticator/MemberLoginForm.php
index e3d345e28..f60fb68b4 100644
--- a/src/Security/MemberAuthenticator/MemberLoginForm.php
+++ b/src/Security/MemberAuthenticator/MemberLoginForm.php
@@ -77,7 +77,7 @@ class MemberLoginForm extends BaseLoginForm
         $checkCurrentUser = true
     ) {
         $this->setController($controller);
-        $this->authenticator_class = $authenticatorClass;
+        $this->setAuthenticatorClass($authenticatorClass);
 
         $customCSS = project() . '/css/member_login.css';
         if (Director::fileExists($customCSS)) {
@@ -88,7 +88,7 @@ class MemberLoginForm extends BaseLoginForm
             // @todo find a more elegant way to handle this
             $logoutAction = Security::logout_url();
             $fields = FieldList::create(
-                HiddenField::create('AuthenticationMethod', null, $this->authenticator_class, $this)
+                HiddenField::create('AuthenticationMethod', null, $this->getAuthenticatorClass(), $this)
             );
             $actions = FieldList::create(
                 FormAction::create('logout', _t(
@@ -133,7 +133,7 @@ class MemberLoginForm extends BaseLoginForm
 
         $label = Member::singleton()->fieldLabel(Member::config()->get('unique_identifier_field'));
         $fields = FieldList::create(
-            HiddenField::create("AuthenticationMethod", null, $this->authenticator_class, $this),
+            HiddenField::create("AuthenticationMethod", null, $this->getAuthenticatorClass(), $this),
             // Regardless of what the unique identifer field is (usually 'Email'), it will be held in the
             // 'Email' value, below:
             // @todo Rename the field to a more generic covering name