diff --git a/lib/Entities/NewsletterEntity.php b/lib/Entities/NewsletterEntity.php
index 4aa27c4d71..38e365da8b 100644
--- a/lib/Entities/NewsletterEntity.php
+++ b/lib/Entities/NewsletterEntity.php
@@ -97,7 +97,7 @@ class NewsletterEntity {
   private $preheader = '';
 
   /**
-   * @ORM\Column(type="json")
+   * @ORM\Column(type="json", nullable=true)
    * @var array|null
    */
   private $body;
diff --git a/lib/Entities/NewsletterTemplateEntity.php b/lib/Entities/NewsletterTemplateEntity.php
index b7b8d5ba59..b859ba5028 100644
--- a/lib/Entities/NewsletterTemplateEntity.php
+++ b/lib/Entities/NewsletterTemplateEntity.php
@@ -39,7 +39,7 @@ class NewsletterTemplateEntity {
   private $categories = '[]';
 
   /**
-   * @ORM\Column(type="json")
+   * @ORM\Column(type="json", nullable=true)
    * @Assert\NotBlank()
    * @var array|null
    */
diff --git a/lib/Entities/ScheduledTaskEntity.php b/lib/Entities/ScheduledTaskEntity.php
index 2f8432b821..28a7abc6c4 100644
--- a/lib/Entities/ScheduledTaskEntity.php
+++ b/lib/Entities/ScheduledTaskEntity.php
@@ -58,7 +58,7 @@ class ScheduledTaskEntity {
   private $processedAt;
 
   /**
-   * @ORM\Column(type="json")
+   * @ORM\Column(type="json", nullable=true)
    * @var array|null
    */
   private $meta;
diff --git a/lib/Entities/SendingQueueEntity.php b/lib/Entities/SendingQueueEntity.php
index 27add5e3cd..5821a5b317 100644
--- a/lib/Entities/SendingQueueEntity.php
+++ b/lib/Entities/SendingQueueEntity.php
@@ -72,7 +72,7 @@ class SendingQueueEntity {
   private $countToProcess = 0;
 
   /**
-   * @ORM\Column(type="json")
+   * @ORM\Column(type="json", nullable=true)
    * @var array|null
    */
   private $meta;
diff --git a/lib/Entities/SubscriberEntity.php b/lib/Entities/SubscriberEntity.php
index 01a21a1474..12e52a937a 100644
--- a/lib/Entities/SubscriberEntity.php
+++ b/lib/Entities/SubscriberEntity.php
@@ -30,7 +30,7 @@ class SubscriberEntity {
 
   /**
    * @ORM\Column(type="bigint", nullable=true)
-   * @var int|null
+   * @var string|null
    */
   private $wpUserId;
 
@@ -133,14 +133,14 @@ class SubscriberEntity {
    * @return int|null
    */
   public function getWpUserId() {
-    return $this->wpUserId;
+    return $this->wpUserId ? (int)$this->wpUserId : null;
   }
 
   /**
    * @param int|null $wpUserId
    */
   public function setWpUserId($wpUserId) {
-    $this->wpUserId = $wpUserId;
+    $this->wpUserId = $wpUserId ? (string)$wpUserId : null;
   }
 
   /**