diff --git a/src/Feature/Contacts/ContactsFeature.php b/src/Feature/Contacts/ContactsFeature.php
index df9de39..b15d7bf 100644
--- a/src/Feature/Contacts/ContactsFeature.php
+++ b/src/Feature/Contacts/ContactsFeature.php
@@ -18,10 +18,10 @@
 interface ContactsFeature
 {
     /**
+     * @param FindContactsBag|null $findContactsBag
      * @return Contact[]
-     * @todo method signature to be changed in next major release as implicitly marking parameter as nullable is deprecated since PHP 8.4
      */
-    public function findContacts(FindContactsBag $findContactsBag = null): array;
+    public function findContacts($findContactsBag = null): array;
 
     public function findContact(FindContactBag $findContactBag): Contact;
 
diff --git a/src/Feature/Contacts/ContactsHttpFeature.php b/src/Feature/Contacts/ContactsHttpFeature.php
index 7c73a56..4f58f9d 100644
--- a/src/Feature/Contacts/ContactsHttpFeature.php
+++ b/src/Feature/Contacts/ContactsHttpFeature.php
@@ -32,9 +32,9 @@ public function __construct(RestRequestExecutor $restRequestExecutor, DataFactor
     }
 
     /**
-     * @todo method signature to be changed in next major release as implicitly marking parameter as nullable is deprecated since PHP 8.4
+     * @param FindContactsBag|null $findContactsBag
      */
-    public function findContacts(FindContactsBag $findContactsBag = null): array
+    public function findContacts($findContactsBag = null): array
     {
         $result = $this->restRequestExecutor->read('contacts', (array)$findContactsBag);
 
diff --git a/src/Feature/Sms/Bag/ScheduleSmsBag.php b/src/Feature/Sms/Bag/ScheduleSmsBag.php
index 2ce4b52..28a1576 100644
--- a/src/Feature/Sms/Bag/ScheduleSmsBag.php
+++ b/src/Feature/Sms/Bag/ScheduleSmsBag.php
@@ -68,9 +68,9 @@ public function setParams(array $params): self
     }
 
     /**
-     * @todo method signature to be changed in next major release as implicitly marking parameter as nullable is deprecated since PHP 8.4
+     * @param bool|null $checkIdx
      */
-    public function setExternalId(string $idx, bool $checkIdx = null): self
+    public function setExternalId(string $idx, $checkIdx = null): self
     {
         $this->idx = [$idx];
         $this->checkIdx = $checkIdx;
@@ -82,7 +82,10 @@ public function setExternalId(string $idx, bool $checkIdx = null): self
      * @deprecated
      * @see ScheduleSmsBag::setExternalId()
      */
-    public function setIdx(array $idx, bool $checkIdx = null): self
+    /**
+     * @param bool|null $checkIdx
+     */
+    public function setIdx(array $idx, $checkIdx = null): self
     {
         $this->idx = $idx;
         $this->checkIdx = $checkIdx;
diff --git a/src/Feature/Sms/Bag/ScheduleSmsToGroupBag.php b/src/Feature/Sms/Bag/ScheduleSmsToGroupBag.php
index 0981fd2..d10e61f 100644
--- a/src/Feature/Sms/Bag/ScheduleSmsToGroupBag.php
+++ b/src/Feature/Sms/Bag/ScheduleSmsToGroupBag.php
@@ -56,9 +56,9 @@ public static function withTemplateName(DateTimeInterface $scheduleAt, string $g
     }
 
     /**
-     * @todo method signature to be changed in next major release as implicitly marking parameter as nullable is deprecated since PHP 8.4
+     * @param bool|null $checkIdx
      */
-    public function setExternalId(string $idx, bool $checkIdx = null): self
+    public function setExternalId(string $idx, $checkIdx = null): self
     {
         $this->idx = [$idx];
         $this->checkIdx = $checkIdx;
@@ -70,7 +70,10 @@ public function setExternalId(string $idx, bool $checkIdx = null): self
      * @deprecated
      * @see ScheduleSmsToGroupBag::setExternalId()
      */
-    public function setIdx(array $idx, bool $checkIdx = null): self
+    /**
+     * @param bool|null $checkIdx
+     */
+    public function setIdx(array $idx, $checkIdx = null): self
     {
         $this->idx = $idx;
         $this->checkIdx = $checkIdx;
diff --git a/src/Feature/Sms/Bag/ScheduleSmssBag.php b/src/Feature/Sms/Bag/ScheduleSmssBag.php
index b214567..82330ec 100644
--- a/src/Feature/Sms/Bag/ScheduleSmssBag.php
+++ b/src/Feature/Sms/Bag/ScheduleSmssBag.php
@@ -69,9 +69,9 @@ public function setParams(array $params): self
     }
 
     /**
-     * @todo method signature to be changed in next major release as implicitly marking parameter as nullable is deprecated since PHP 8.4
+     * @param bool|null $checkIdx
      */
-    public function setExternalId(array $idx, bool $checkIdx = null): self
+    public function setExternalId(array $idx, $checkIdx = null): self
     {
         $this->idx = $idx;
         $this->checkIdx = $checkIdx;
diff --git a/src/Feature/Sms/Bag/SendSmsBag.php b/src/Feature/Sms/Bag/SendSmsBag.php
index 9ac48b5..7db1b52 100644
--- a/src/Feature/Sms/Bag/SendSmsBag.php
+++ b/src/Feature/Sms/Bag/SendSmsBag.php
@@ -63,9 +63,9 @@ public function setParams(array $params): self
     }
 
     /**
-     * @todo method signature to be changed in next major release as implicitly marking parameter as nullable is deprecated since PHP 8.4
+     * @param bool|null $checkIdx
      */
-    public function setExternalId(string $idx, bool $checkIdx = null): self
+    public function setExternalId(string $idx, $checkIdx = null): self
     {
         $this->idx = [$idx];
         $this->checkIdx = $checkIdx;
diff --git a/src/Feature/Sms/Bag/SendSmsToGroupBag.php b/src/Feature/Sms/Bag/SendSmsToGroupBag.php
index a6da846..fadfbc7 100644
--- a/src/Feature/Sms/Bag/SendSmsToGroupBag.php
+++ b/src/Feature/Sms/Bag/SendSmsToGroupBag.php
@@ -49,9 +49,9 @@ public static function withTemplateName(string $group, string $templateName): se
     }
 
     /**
-     * @todo method signature to be changed in next major release as implicitly marking parameter as nullable is deprecated since PHP 8.4
+     * @param bool|null $checkIdx
      */
-    public function setExternalId(string $idx, bool $checkIdx = null): self
+    public function setExternalId(string $idx, $checkIdx = null): self
     {
         $this->idx = [$idx];
         $this->checkIdx = $checkIdx;
@@ -63,7 +63,10 @@ public function setExternalId(string $idx, bool $checkIdx = null): self
      * @deprecated
      * @see SendSmsToGroupBag::setExternalId()
      */
-    public function setIdx(array $idx, bool $checkIdx = null): self
+    /**
+     * @param bool|null $checkIdx
+     */
+    public function setIdx(array $idx, $checkIdx = null): self
     {
         $this->idx = $idx;
         $this->checkIdx = $checkIdx;
diff --git a/src/Feature/Sms/Bag/SendSmssBag.php b/src/Feature/Sms/Bag/SendSmssBag.php
index 279bc53..ae4b067 100644
--- a/src/Feature/Sms/Bag/SendSmssBag.php
+++ b/src/Feature/Sms/Bag/SendSmssBag.php
@@ -64,9 +64,9 @@ public function setParams(array $params): self
     }
 
     /**
-     * @todo method signature to be changed in next major release as implicitly marking parameter as nullable is deprecated since PHP 8.4
+     * @param bool|null $checkIdx
      */
-    public function setExternalId(array $idx, bool $checkIdx = null): self
+    public function setExternalId(array $idx, $checkIdx = null): self
     {
         $this->idx = $idx;
         $this->checkIdx = $checkIdx;