diff --git a/mailpoet/lib/Subscription/Captcha/CaptchaSession.php b/mailpoet/lib/Subscription/Captcha/CaptchaSession.php
index ce16161d2d..bda4e8651b 100644
--- a/mailpoet/lib/Subscription/Captcha/CaptchaSession.php
+++ b/mailpoet/lib/Subscription/Captcha/CaptchaSession.php
@@ -15,8 +15,8 @@ class CaptchaSession {
   /** @var WPFunctions */
   private $wp;
 
-  /** @var ?string */
-  private $id = null;
+  /** @var string */
+  private $id = '';
 
   public function __construct(
     WPFunctions $wp
@@ -24,11 +24,14 @@ class CaptchaSession {
     $this->wp = $wp;
   }
 
-  public function init($id = null) {
+  public function init(string $id = null) {
     $this->id = $id ?: Security::generateRandomString(self::ID_LENGTH);
   }
 
-  public function getId(): ?string {
+  public function getId(): string {
+    if (!$this->id) {
+      $this->init();
+    }
     return $this->id;
   }
 
diff --git a/mailpoet/lib/Subscription/Captcha/Validator/BuiltInCaptchaValidator.php b/mailpoet/lib/Subscription/Captcha/Validator/BuiltInCaptchaValidator.php
index 5a82f5a370..25ccfa0487 100644
--- a/mailpoet/lib/Subscription/Captcha/Validator/BuiltInCaptchaValidator.php
+++ b/mailpoet/lib/Subscription/Captcha/Validator/BuiltInCaptchaValidator.php
@@ -56,7 +56,7 @@ class BuiltInCaptchaValidator implements CaptchaValidator {
       throw new ValidationError(
         __('Please fill in the CAPTCHA.', 'mailpoet'),
         [
-          'redirect_url' => $this->subscriptionUrlFactory->getCaptchaUrl($this->getSessionId()),
+          'redirect_url' => $this->subscriptionUrlFactory->getCaptchaUrl($this->captchaSession->getId()),
         ]
       );
     }
@@ -65,7 +65,7 @@ class BuiltInCaptchaValidator implements CaptchaValidator {
       throw new ValidationError(
         __('Please regenerate the CAPTCHA.', 'mailpoet'),
         [
-          'redirect_url' => $this->subscriptionUrlFactory->getCaptchaUrl($this->getSessionId()),
+          'redirect_url' => $this->subscriptionUrlFactory->getCaptchaUrl($this->captchaSession->getId()),
         ]
       );
     }
@@ -84,15 +84,6 @@ class BuiltInCaptchaValidator implements CaptchaValidator {
 
   }
 
-  private function getSessionId() {
-    $id = $this->captchaSession->getId();
-    if ($id === null) {
-      $this->captchaSession->init();
-      $id = $this->captchaSession->getId();
-    }
-    return $id;
-  }
-
   public function isRequired($subscriberEmail = null) {
     if ($this->isUserExemptFromCaptcha()) {
       return false;