diff --git a/src/CodeHelper/Methods/JsonSerializeMethod.php b/src/CodeHelper/Methods/JsonSerializeMethod.php
index 7666267..b00c793 100644
--- a/src/CodeHelper/Methods/JsonSerializeMethod.php
+++ b/src/CodeHelper/Methods/JsonSerializeMethod.php
@@ -18,7 +18,7 @@
  */
 final class JsonSerializeMethod extends PhpMethod
 {
-	public static function fromClass(PhpClass $class, TypeCallResolverInterface $resolver = null): self
+	public static function fromClass(PhpClass $class, ?TypeCallResolverInterface $resolver = null): self
 	{
 		$resolver = $resolver ?? new JsonSerializeTypeCallResolver();
 
diff --git a/src/PhpFile.php b/src/PhpFile.php
index e9ae1d1..b47c703 100644
--- a/src/PhpFile.php
+++ b/src/PhpFile.php
@@ -139,7 +139,7 @@ public function addFunction(PhpFunction $function): self
 	/**
 	 * Add use statement after namespace declaration
 	 */
-	public function addUse(Identifier|string $identifier, string $alias = null): self
+	public function addUse(Identifier|string $identifier, ?string $alias = null): self
 	{
 		$identifier = Identifier::fromUnknown($identifier);
 		if ($alias) {
diff --git a/src/PhpMethod.php b/src/PhpMethod.php
index 82289fb..21fbf11 100644
--- a/src/PhpMethod.php
+++ b/src/PhpMethod.php
@@ -113,7 +113,7 @@ public static function getter(PhpVariable $var, array $source = []): self
 	 * @param PhpParam[] $params
 	 * @param array<array-key, string|string[]> $source
 	 */
-	public static function public(string $identifier, array $params, array $source, Type $type = null): self
+	public static function public(string $identifier, array $params, array $source, ?Type $type = null): self
 	{
 		return new self(self::PUBLIC_ACCESS, $identifier, $params, $source, $type ?? Type::empty());
 	}
@@ -122,7 +122,7 @@ public static function public(string $identifier, array $params, array $source,
 	 * @param PhpParam[] $params
 	 * @param array<array-key, string|string[]> $source
 	 */
-	public static function private(string $identifier, array $params, array $source, Type $type = null): self
+	public static function private(string $identifier, array $params, array $source, ?Type $type = null): self
 	{
 		return new self(self::PRIVATE_ACCESS, $identifier, $params, $source, $type ?? Type::empty());
 	}
@@ -131,7 +131,7 @@ public static function private(string $identifier, array $params, array $source,
 	 * @param PhpParam[] $params
 	 * @param array<array-key, string|string[]> $source
 	 */
-	public static function protected(string $identifier, array $params, array $source, Type $type = null): self
+	public static function protected(string $identifier, array $params, array $source, ?Type $type = null): self
 	{
 		return new self(self::PROTECTED_ACCESS, $identifier, $params, $source, $type ?? Type::empty());
 	}
diff --git a/src/PhpTrait.php b/src/PhpTrait.php
index 5e3ffba..dd6dd13 100644
--- a/src/PhpTrait.php
+++ b/src/PhpTrait.php
@@ -54,7 +54,7 @@ public function getComment(): PhpDocComment
 		return $this->comment;
 	}
 
-	public function addUse(Identifier|string $class, string $alias = null): static
+	public function addUse(Identifier|string $class, ?string $alias = null): static
 	{
 		$class = Identifier::fromUnknown($class);
 		if (!$alias && $this->identifier->equal($class)) {