diff --git a/mailpoet/lib/Automation/Engine/Data/WorkflowRunLog.php b/mailpoet/lib/Automation/Engine/Data/WorkflowRunLog.php
index 7283226923..dfb3a6c4cb 100644
--- a/mailpoet/lib/Automation/Engine/Data/WorkflowRunLog.php
+++ b/mailpoet/lib/Automation/Engine/Data/WorkflowRunLog.php
@@ -91,10 +91,7 @@ class WorkflowRunLog {
     return $this->data;
   }
 
-  /**
-   * @return DateTimeImmutable|null
-   */
-  public function getCompletedAt() {
+  public function getCompletedAt(): ?DateTimeImmutable {
     return $this->completedAt;
   }