diff --git a/UPGRADE-5.3.md b/UPGRADE-5.3.md
index 2ccc3bc039..cd7dda750e 100644
--- a/UPGRADE-5.3.md
+++ b/UPGRADE-5.3.md
@@ -23,6 +23,11 @@ HttpKernel
 
  * Marked the class `Symfony\Component\HttpKernel\EventListener\DebugHandlersListener` as internal
 
+Notifier
+-------
+
+* Changed the return type of `Symfony\Component\Notifier\Transport\AbstractTransportFactory::getEndpoint()` from `?string` to `string`
+
 PhpunitBridge
 -------------
 
diff --git a/src/Symfony/Component/Notifier/Bridge/Infobip/InfobipTransport.php b/src/Symfony/Component/Notifier/Bridge/Infobip/InfobipTransport.php
index df76522386..32984b3c2f 100644
--- a/src/Symfony/Component/Notifier/Bridge/Infobip/InfobipTransport.php
+++ b/src/Symfony/Component/Notifier/Bridge/Infobip/InfobipTransport.php
@@ -85,7 +85,7 @@ final class InfobipTransport extends AbstractTransport
         return new SentMessage($message, (string) $this);
     }
 
-    protected function getEndpoint(): ?string
+    protected function getEndpoint(): string
     {
         return $this->host.($this->port ? ':'.$this->port : '');
     }
diff --git a/src/Symfony/Component/Notifier/Bridge/Mattermost/MattermostTransport.php b/src/Symfony/Component/Notifier/Bridge/Mattermost/MattermostTransport.php
index 59730b97f7..6a718b9145 100644
--- a/src/Symfony/Component/Notifier/Bridge/Mattermost/MattermostTransport.php
+++ b/src/Symfony/Component/Notifier/Bridge/Mattermost/MattermostTransport.php
@@ -85,7 +85,7 @@ final class MattermostTransport extends AbstractTransport
         return $sentMessage;
     }
 
-    protected function getEndpoint(): ?string
+    protected function getEndpoint(): string
     {
         return rtrim($this->host.($this->port ? ':'.$this->port : '').($this->path ?? ''), '/');
     }
diff --git a/src/Symfony/Component/Notifier/CHANGELOG.md b/src/Symfony/Component/Notifier/CHANGELOG.md
index 528aa24018..f6106137d9 100644
--- a/src/Symfony/Component/Notifier/CHANGELOG.md
+++ b/src/Symfony/Component/Notifier/CHANGELOG.md
@@ -5,6 +5,7 @@ CHANGELOG
 -----
 
  * The component is not marked as `@experimental` anymore
+* [BC BREAK] Changed the return type of `AbstractTransportFactory::getEndpoint()` from `?string` to `string`
 
 5.2.0
 -----
diff --git a/src/Symfony/Component/Notifier/Transport/AbstractTransport.php b/src/Symfony/Component/Notifier/Transport/AbstractTransport.php
index ccb1f8c840..670fd49847 100644
--- a/src/Symfony/Component/Notifier/Transport/AbstractTransport.php
+++ b/src/Symfony/Component/Notifier/Transport/AbstractTransport.php
@@ -79,7 +79,7 @@ abstract class AbstractTransport implements TransportInterface
 
     abstract protected function doSend(MessageInterface $message): SentMessage;
 
-    protected function getEndpoint(): ?string
+    protected function getEndpoint(): string
     {
         return ($this->host ?: $this->getDefaultHost()).($this->port ? ':'.$this->port : '');
     }