diff --git a/mailpoet/lib/Automation/Engine/Registry.php b/mailpoet/lib/Automation/Engine/Registry.php
index 80fb7e1cf3..f9fa4786cf 100644
--- a/mailpoet/lib/Automation/Engine/Registry.php
+++ b/mailpoet/lib/Automation/Engine/Registry.php
@@ -4,6 +4,7 @@ namespace MailPoet\Automation\Engine;
 
 use MailPoet\Automation\Engine\Control\RootStep;
 use MailPoet\Automation\Engine\Workflows\Action;
+use MailPoet\Automation\Engine\Workflows\Payload;
 use MailPoet\Automation\Engine\Workflows\Step;
 use MailPoet\Automation\Engine\Workflows\Subject;
 use MailPoet\Automation\Engine\Workflows\Trigger;
@@ -12,7 +13,7 @@ class Registry {
   /** @var array<string, Step> */
   private $steps = [];
 
-  /** @var array<string, Subject> */
+  /** @var array<string, Subject<Payload>> */
   private $subjects = [];
 
   /** @var array<string, Trigger> */
@@ -32,6 +33,7 @@ class Registry {
     $this->steps[$rootStep->getKey()] = $rootStep;
   }
 
+  /** @param Subject<Payload> $subject */
   public function addSubject(Subject $subject): void {
     $key = $subject->getKey();
     if (isset($this->subjects[$key])) {
@@ -40,11 +42,12 @@ class Registry {
     $this->subjects[$key] = $subject;
   }
 
+  /** @return Subject<Payload>|null */
   public function getSubject(string $key): ?Subject {
     return $this->subjects[$key] ?? null;
   }
 
-  /** @return array<string, Subject> */
+  /** @return array<string, Subject<Payload>> */
   public function getSubjects(): array {
     return $this->subjects;
   }
diff --git a/mailpoet/lib/Automation/Engine/Workflows/Payload.php b/mailpoet/lib/Automation/Engine/Workflows/Payload.php
new file mode 100644
index 0000000000..fa73af8718
--- /dev/null
+++ b/mailpoet/lib/Automation/Engine/Workflows/Payload.php
@@ -0,0 +1,6 @@
+<?php declare(strict_types = 1);
+
+namespace MailPoet\Automation\Engine\Workflows;
+
+interface Payload {
+}
diff --git a/mailpoet/lib/Automation/Engine/Workflows/Subject.php b/mailpoet/lib/Automation/Engine/Workflows/Subject.php
index 2084f6d1bf..d0a2552ef1 100644
--- a/mailpoet/lib/Automation/Engine/Workflows/Subject.php
+++ b/mailpoet/lib/Automation/Engine/Workflows/Subject.php
@@ -2,13 +2,19 @@
 
 namespace MailPoet\Automation\Engine\Workflows;
 
+use MailPoet\Automation\Engine\Data\Subject as SubjectData;
+use MailPoet\Validator\Schema\ObjectSchema;
+
+/**
+ * @template-covariant T of Payload
+ */
 interface Subject {
   public function getKey(): string;
 
-  /** array<SubjectField> */
-  public function getFields(): array;
+  public function getName(): string;
 
-  public function load(array $args): void;
+  public function getArgsSchema(): ObjectSchema;
 
-  public function pack(): array;
+  /** @return T */
+  public function getPayload(SubjectData $subjectData): Payload;
 }