diff --git a/mailpoet/lib/Automation/Engine/Control/RootStep.php b/mailpoet/lib/Automation/Engine/Control/RootStep.php
index 2c1a33d9eb..cff0af4bd3 100644
--- a/mailpoet/lib/Automation/Engine/Control/RootStep.php
+++ b/mailpoet/lib/Automation/Engine/Control/RootStep.php
@@ -17,4 +17,8 @@ class RootStep implements Step {
   public function getArgsSchema(): ObjectSchema {
     return new ObjectSchema();
   }
+
+  public function getSubjectKeys(): array {
+    return [];
+  }
 }
diff --git a/mailpoet/lib/Automation/Engine/Workflows/Step.php b/mailpoet/lib/Automation/Engine/Workflows/Step.php
index 483570a3f7..6de9fd81d4 100644
--- a/mailpoet/lib/Automation/Engine/Workflows/Step.php
+++ b/mailpoet/lib/Automation/Engine/Workflows/Step.php
@@ -10,4 +10,7 @@ interface Step {
   public function getName(): string;
 
   public function getArgsSchema(): ObjectSchema;
+
+  /** @return string[] */
+  public function getSubjectKeys(): array;
 }
diff --git a/mailpoet/lib/Automation/Integrations/Core/Actions/DelayAction.php b/mailpoet/lib/Automation/Integrations/Core/Actions/DelayAction.php
index 074e8b65f9..0a0dbbea56 100644
--- a/mailpoet/lib/Automation/Integrations/Core/Actions/DelayAction.php
+++ b/mailpoet/lib/Automation/Integrations/Core/Actions/DelayAction.php
@@ -36,6 +36,10 @@ class DelayAction implements Action {
     ]);
   }
 
+  public function getSubjectKeys(): array {
+    return [];
+  }
+
   public function run(Workflow $workflow, WorkflowRun $workflowRun, Step $step): void {
     $nextStep = $step->getNextSteps()[0] ?? null;
     $this->actionScheduler->schedule(time() + $this->calculateSeconds($step), Hooks::WORKFLOW_STEP, [
diff --git a/mailpoet/lib/Automation/Integrations/MailPoet/Actions/SendEmailAction.php b/mailpoet/lib/Automation/Integrations/MailPoet/Actions/SendEmailAction.php
index 176a4b2e4f..aa51b4819a 100644
--- a/mailpoet/lib/Automation/Integrations/MailPoet/Actions/SendEmailAction.php
+++ b/mailpoet/lib/Automation/Integrations/MailPoet/Actions/SendEmailAction.php
@@ -72,6 +72,13 @@ class SendEmailAction implements Action {
     ]);
   }
 
+  public function getSubjectKeys(): array {
+    return [
+      'mailpoet:segment',
+      'mailpoet:subscriber',
+    ];
+  }
+
   public function isValid(array $subjects, Step $step, Workflow $workflow): bool {
     try {
       $this->getEmailForStep($step);
diff --git a/mailpoet/lib/Automation/Integrations/MailPoet/Triggers/SomeoneSubscribesTrigger.php b/mailpoet/lib/Automation/Integrations/MailPoet/Triggers/SomeoneSubscribesTrigger.php
index 95c26b04be..3d168bba24 100644
--- a/mailpoet/lib/Automation/Integrations/MailPoet/Triggers/SomeoneSubscribesTrigger.php
+++ b/mailpoet/lib/Automation/Integrations/MailPoet/Triggers/SomeoneSubscribesTrigger.php
@@ -39,6 +39,13 @@ class SomeoneSubscribesTrigger implements Trigger {
     ]);
   }
 
+  public function getSubjectKeys(): array {
+    return [
+      SubscriberSubject::KEY,
+      SegmentSubject::KEY,
+    ];
+  }
+
   public function registerHooks(): void {
     $this->wp->addAction('mailpoet_segment_subscribed', [$this, 'handleSubscription'], 10, 2);
   }
diff --git a/mailpoet/tests/integration/Automation/Engine/Data/WorkflowRunLogTest.php b/mailpoet/tests/integration/Automation/Engine/Data/WorkflowRunLogTest.php
index 98411c2702..d2695e69c1 100644
--- a/mailpoet/tests/integration/Automation/Engine/Data/WorkflowRunLogTest.php
+++ b/mailpoet/tests/integration/Automation/Engine/Data/WorkflowRunLogTest.php
@@ -285,6 +285,11 @@ class TestAction implements Action {
     $this->callback = $callback;
   }
 
+
+  public function getSubjectKeys(): array {
+    return [];
+  }
+
   public function isValid(array $subjects, Step $step, Workflow $workflow): bool {
     return true;
   }