diff --git a/src/ResponseFactory.php b/src/ResponseFactory.php
index 125667e9..0c336568 100644
--- a/src/ResponseFactory.php
+++ b/src/ResponseFactory.php
@@ -46,7 +46,7 @@ public function share($key, $value = null): void
         }
     }
 
-    public function getShared(string $key = null, $default = null)
+    public function getShared(?string $key = null, $default = null)
     {
         if ($key) {
             return Arr::get($this->sharedProps, $key, $default);
diff --git a/src/Testing/AssertableInertia.php b/src/Testing/AssertableInertia.php
index 370e748d..22abcbc3 100644
--- a/src/Testing/AssertableInertia.php
+++ b/src/Testing/AssertableInertia.php
@@ -42,7 +42,7 @@ public static function fromTestResponse(TestResponse $response): self
         return $instance;
     }
 
-    public function component(string $value = null, $shouldExist = null): self
+    public function component(?string $value = null, $shouldExist = null): self
     {
         PHPUnit::assertSame($value, $this->component, 'Unexpected Inertia page component.');
 
diff --git a/src/Testing/Concerns/Debugging.php b/src/Testing/Concerns/Debugging.php
index 612374de..86a6269c 100644
--- a/src/Testing/Concerns/Debugging.php
+++ b/src/Testing/Concerns/Debugging.php
@@ -4,17 +4,17 @@
 
 trait Debugging
 {
-    public function dump(string $prop = null): self
+    public function dump(?string $prop = null): self
     {
         dump($this->prop($prop));
 
         return $this;
     }
 
-    public function dd(string $prop = null): void
+    public function dd(?string $prop = null): void
     {
         dd($this->prop($prop));
     }
 
-    abstract protected function prop(string $key = null);
+    abstract protected function prop(?string $key = null);
 }
diff --git a/src/Testing/Concerns/Has.php b/src/Testing/Concerns/Has.php
index acfad9df..d181dae3 100644
--- a/src/Testing/Concerns/Has.php
+++ b/src/Testing/Concerns/Has.php
@@ -38,7 +38,7 @@ public function hasAll($key): self
     /**
      * @return $this
      */
-    public function has(string $key, $value = null, Closure $scope = null): self
+    public function has(string $key, $value = null, ?Closure $scope = null): self
     {
         PHPUnit::assertTrue(
             Arr::has($this->prop(), $key),
@@ -106,7 +106,7 @@ public function misses(string $key): self
         return $this->missing($key);
     }
 
-    abstract protected function prop(string $key = null);
+    abstract protected function prop(?string $key = null);
 
     abstract protected function dotPath(string $key): string;
 
diff --git a/src/Testing/Concerns/Interaction.php b/src/Testing/Concerns/Interaction.php
index 506d64d2..145d405e 100644
--- a/src/Testing/Concerns/Interaction.php
+++ b/src/Testing/Concerns/Interaction.php
@@ -37,5 +37,5 @@ public function etc(): self
         return $this;
     }
 
-    abstract protected function prop(string $key = null);
+    abstract protected function prop(?string $key = null);
 }
diff --git a/src/Testing/Concerns/Matching.php b/src/Testing/Concerns/Matching.php
index 6cb4404b..17f8d942 100644
--- a/src/Testing/Concerns/Matching.php
+++ b/src/Testing/Concerns/Matching.php
@@ -68,7 +68,7 @@ protected function ensureSorted(&$value): void
 
     abstract protected function dotPath(string $key): string;
 
-    abstract protected function prop(string $key = null);
+    abstract protected function prop(?string $key = null);
 
-    abstract public function has(string $key, $value = null, Closure $scope = null);
+    abstract public function has(string $key, $value = null, ?Closure $scope = null);
 }
diff --git a/src/Testing/Concerns/PageObject.php b/src/Testing/Concerns/PageObject.php
index 1dc98389..467c48c3 100644
--- a/src/Testing/Concerns/PageObject.php
+++ b/src/Testing/Concerns/PageObject.php
@@ -8,7 +8,7 @@
 
 trait PageObject
 {
-    public function component(string $value = null, $shouldExist = null): self
+    public function component(?string $value = null, $shouldExist = null): self
     {
         PHPUnit::assertSame($value, $this->component, 'Unexpected Inertia page component.');
 
@@ -23,7 +23,7 @@ public function component(string $value = null, $shouldExist = null): self
         return $this;
     }
 
-    protected function prop(string $key = null)
+    protected function prop(?string $key = null)
     {
         return Arr::get($this->props, $key);
     }
diff --git a/src/Testing/TestResponseMacros.php b/src/Testing/TestResponseMacros.php
index a4ca6802..428dc2a6 100644
--- a/src/Testing/TestResponseMacros.php
+++ b/src/Testing/TestResponseMacros.php
@@ -8,7 +8,7 @@ class TestResponseMacros
 {
     public function assertInertia()
     {
-        return function (Closure $callback = null) {
+        return function (?Closure $callback = null) {
             $assert = AssertableInertia::fromTestResponse($this);
 
             if (is_null($callback)) {