diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 7fa0ea1..420cb9b 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -39,6 +39,8 @@ jobs:
           - "8.0"
           - "8.1"
           - "8.2"
+          - "8.3"
+          - "8.4"
 
     steps:
       - name: Checkout.
diff --git a/.github/workflows/static.yml b/.github/workflows/static.yml
index 3e79b31..0d90f64 100644
--- a/.github/workflows/static.yml
+++ b/.github/workflows/static.yml
@@ -35,6 +35,7 @@ jobs:
           - "8.0"
           - "8.1"
           - "8.2"
+          - "8.3"
 
     steps:
       - name: Checkout.
diff --git a/src/Route.php b/src/Route.php
index 546adc8..3790eea 100644
--- a/src/Route.php
+++ b/src/Route.php
@@ -337,7 +337,7 @@ public function path(array $parameters = []): string
      * @throws InvalidRouteParameterException If the host or the parameter value does not match its regexp.
      * @psalm-suppress PossiblyNullArgument
      */
-    public function url(array $parameters = [], string $host = null, bool $secure = null): string
+    public function url(array $parameters = [], ?string $host = null, ?bool $secure = null): string
     {
         $path = $this->path($parameters);
         $host = $host ? trim($host, '/') : null;
diff --git a/src/RouteCollection.php b/src/RouteCollection.php
index 6e4c56c..b8ca92b 100644
--- a/src/RouteCollection.php
+++ b/src/RouteCollection.php
@@ -135,7 +135,7 @@ public function path(string $name, array $parameters = []): string
     /**
      * {@inheritDoc}
      */
-    public function url(string $name, array $parameters = [], string $host = null, bool $secure = null): string
+    public function url(string $name, array $parameters = [], ?string $host = null, ?bool $secure = null): string
     {
         $route = $this->get($name);
         return $route->url($parameters, $host, $secure);
diff --git a/src/RouteCollectionInterface.php b/src/RouteCollectionInterface.php
index 688daa6..b0e587c 100644
--- a/src/RouteCollectionInterface.php
+++ b/src/RouteCollectionInterface.php
@@ -90,5 +90,5 @@ public function path(string $name, array $parameters = []): string;
      * @return string URL generated.
      * @throws RouteNotFoundException if the route does not exist.
      */
-    public function url(string $name, array $parameters = [], string $host = null, bool $secure = null): string;
+    public function url(string $name, array $parameters = [], ?string $host = null, ?bool $secure = null): string;
 }
diff --git a/src/RouteCollector.php b/src/RouteCollector.php
index 8f52233..f781994 100644
--- a/src/RouteCollector.php
+++ b/src/RouteCollector.php
@@ -19,7 +19,7 @@ final class RouteCollector
     /**
      * @param RouteCollectionInterface|null $routes
      */
-    public function __construct(RouteCollectionInterface $routes = null)
+    public function __construct(?RouteCollectionInterface $routes = null)
     {
         $this->routes = $routes ?? new RouteCollection();
     }