diff --git a/code/Model/Recipient/EmailRecipient.php b/code/Model/Recipient/EmailRecipient.php
index 01ae893..e95d72e 100644
--- a/code/Model/Recipient/EmailRecipient.php
+++ b/code/Model/Recipient/EmailRecipient.php
@@ -128,17 +128,24 @@ class EmailRecipient extends DataObject
     /**
      * Get instance of UserForm when editing in getCMSFields
      *
-     * @return UserDefinedForm|UserForm
+     * @return UserDefinedForm|UserForm|null
      */
     protected function getFormParent()
     {
+        // If polymorphic relationship is actually defined, use it
+        if ($this->FormID && $this->FormClass) {
+            $formClass = $this->FormClass;
+            return $formClass::get()->byID($this->FormID);
+        }
+
+        // Revert to checking for a form from the session
         // LeftAndMain::sessionNamespace is protected. @todo replace this with a non-deprecated equivalent.
         $sessionNamespace = $this->config()->get('session_namespace') ?: CMSMain::class;
 
-        $formID = $this->FormID ?: Controller::curr()->getRequest()->getSession()->get($sessionNamespace . '.currentPage');
-        $formClass = $this->FormClass ?: UserDefinedForm::class;
-
-        return $formClass::get()->byID($formID);
+        $formID = Controller::curr()->getRequest()->getSession()->get($sessionNamespace . '.currentPage');
+        if ($formID) {
+            return UserDefinedForm::get()->byID($formID);
+        }
     }
 
     public function getTitle()
diff --git a/tests/Control/UserDefinedFormControllerTest.php b/tests/Control/UserDefinedFormControllerTest.php
index 6e2fc5a..f4f6171 100644
--- a/tests/Control/UserDefinedFormControllerTest.php
+++ b/tests/Control/UserDefinedFormControllerTest.php
@@ -2,6 +2,7 @@
 
 namespace SilverStripe\UserForms\Tests\Control;
 
+use SilverStripe\Control\HTTPResponse;
 use SilverStripe\Core\Config\Config;
 use SilverStripe\Dev\CSSContentParser;
 use SilverStripe\Dev\FunctionalTest;
@@ -104,32 +105,26 @@ class UserDefinedFormControllerTest extends FunctionalTest
 
         // Post with no fields
         $this->get($form->URLSegment);
+        /** @var HTTPResponse $response */
         $response = $this->submitForm('UserForm_Form_' . $form->ID, null, []);
-        $this->assertPartialMatchBySelector(
-            '.field .message',
-            ['This field is required']
-        );
+        $this->assertContains('This field is required', $response->getBody());
 
         // Post with all fields, but invalid email
         $this->get($form->URLSegment);
-        $this->submitForm('UserForm_Form_' . $form->ID, null, [
+        /** @var HTTPResponse $response */
+        $response = $this->submitForm('UserForm_Form_' . $form->ID, null, [
             'required-email' => 'invalid',
             'required-text' => 'bob'
         ]);
-        $this->assertPartialMatchBySelector(
-            '.field .message',
-            ['Please enter an email address']
-        );
+        $this->assertContains('Please enter an email address', $response->getBody());
 
         // Post with only required
         $this->get($form->URLSegment);
-        $this->submitForm('UserForm_Form_' . $form->ID, null, [
+        /** @var HTTPResponse $response */
+        $response = $this->submitForm('UserForm_Form_' . $form->ID, null, [
             'required-text' => 'bob'
         ]);
-        $this->assertPartialMatchBySelector(
-            'p',
-            ["Thanks, we've received your submission."]
-        );
+        $this->assertContains("Thanks, we've received your submission.", $response->getBody());
     }
 
     public function testFinished()
diff --git a/tests/Model/UserDefinedFormTest.php b/tests/Model/UserDefinedFormTest.php
index 625ad42..0658071 100644
--- a/tests/Model/UserDefinedFormTest.php
+++ b/tests/Model/UserDefinedFormTest.php
@@ -111,6 +111,7 @@ class UserDefinedFormTest extends FunctionalTest
 
         $popup = new EmailRecipient();
         $popup->FormID = $form->ID;
+        $popup->FormClass = UserDefinedForm::class;
 
         $fields = $popup->getCMSFields();
 
@@ -167,6 +168,7 @@ class UserDefinedFormTest extends FunctionalTest
         $page = $this->objFromFixture(UserDefinedForm::class, 'basic-form-page');
         $recipient = new EmailRecipient();
         $recipient->FormID = $page->ID;
+        $recipient->FormClass = UserDefinedForm::class;
 
         $result = $recipient->getEmailTemplateDropdownValues();
 
@@ -180,6 +182,7 @@ class UserDefinedFormTest extends FunctionalTest
         $page = $this->objFromFixture(UserDefinedForm::class, 'basic-form-page');
         $recipient = new EmailRecipient();
         $recipient->FormID = $page->ID;
+        $recipient->FormClass = UserDefinedForm::class;
 
         // Set the default template
         $recipient->EmailTemplate = current(array_keys($recipient->getEmailTemplateDropdownValues()));