diff --git a/composer.json b/composer.json
index dd9730d..0009490 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,7 @@
     },
     "require-dev": {
         "ergebnis/composer-normalize": "^2.0",
-        "infection/infection": "^0.16",
+        "infection/infection": "^0.21",
         "orchestra/testbench": "^6.0",
         "phpstan/phpstan": "^0.12",
         "phpunit/phpunit": "^9.0",
diff --git a/infection.json.dist b/infection.json.dist
index 7b603a5..0387cbc 100644
--- a/infection.json.dist
+++ b/infection.json.dist
@@ -11,6 +11,11 @@
         }
     },
     "mutators": {
-        "@default": true
+        "@default": true,
+        "InstanceOf_": {
+            "ignoreSourceCodeByRegex": [
+                "assert\\(.*\\);"
+            ]
+        }
     }
 }
diff --git a/tests/HasParametersTest.php b/tests/HasParametersTest.php
index a11425a..0eb5d51 100644
--- a/tests/HasParametersTest.php
+++ b/tests/HasParametersTest.php
@@ -7,6 +7,7 @@
 use ErrorException;
 use Illuminate\Support\Collection;
 use Orchestra\Testbench\TestCase;
+use const PHP_MAJOR_VERSION;
 use Tests\Middleware\Basic;
 use Tests\Middleware\Optional;
 use Tests\Middleware\OptionalRequired;
@@ -76,14 +77,26 @@ public function testListDoesNotAcceptSubArray(): void
         Basic::in(['laravel', ['vue', 'react']]);
     }
 
-    public function testListDetectsRequiredParametersThatHaveNotBeenProvided(): void
+    public function testListDetectsRequiredParametersThatHaveNotBeenProvidedAfterAnOptional(): void
     {
+        if (PHP_MAJOR_VERSION >= 8) {
+            $this->markTestSkipped('Tests functionality deprecated in PHP 8.0');
+        }
+
         $this->expectException(TypeError::class);
         $this->expectExceptionMessage('Missing required argument $required for middleware Tests\\Middleware\\OptionalRequired::handle()');
 
         OptionalRequired::in(['laravel']);
     }
 
+    public function testListDetectsRequiredParametersThatHaveNotBeenProvided(): void
+    {
+        $this->expectException(TypeError::class);
+        $this->expectExceptionMessage('Missing required argument $required for middleware Tests\\Middleware\\Required::handle()');
+
+        Required::in([]);
+    }
+
     public function testListDoesNotAcceptAssociativeArray(): void
     {
         $this->expectException(TypeError::class);
@@ -181,11 +194,14 @@ public function testMap(): void
         $result = Variadic::with(['variadic' => false]);
         $this->assertSame('Tests\\Middleware\\Variadic:0', $result);
 
-        $result = OptionalRequired::with(['required' => 'laravel']);
-        $this->assertSame('Tests\\Middleware\\OptionalRequired:default,laravel', $result);
+        if (PHP_MAJOR_VERSION < 8) {
+            // Tests functionality deprecated in PHP 8.0
+            $result = OptionalRequired::with(['required' => 'laravel']);
+            $this->assertSame('Tests\\Middleware\\OptionalRequired:default,laravel', $result);
 
-        $result = OptionalRequired::with(['required' => 'laravel', 'optional' => 'vue']);
-        $this->assertSame('Tests\\Middleware\\OptionalRequired:vue,laravel', $result);
+            $result = OptionalRequired::with(['required' => 'laravel', 'optional' => 'vue']);
+            $this->assertSame('Tests\\Middleware\\OptionalRequired:vue,laravel', $result);
+        }
 
         $result = RequiredOptionalVariadic::with(['required' => 'laravel']);
         $this->assertSame('Tests\\Middleware\\RequiredOptionalVariadic:laravel,default', $result);
@@ -261,6 +277,10 @@ public function testVariadicDoesNotAcceptSubArray(): void
 
     public function testMiddlewareThatUsesFuncGetArgsCanAccessArgumentsThatAreNotPassedAsParameters(): void
     {
+        if (PHP_MAJOR_VERSION >= 8) {
+            $this->markTestSkipped('Tests functionality deprecated in PHP 8.0');
+        }
+
         $result = OptionalRequired::in(['laravel', 'vue', 'tailwind']);
         $this->assertSame('Tests\\Middleware\\OptionalRequired:laravel,vue,tailwind', $result);
     }
diff --git a/tests/Middleware/OptionalRequired.php b/tests/Middleware/OptionalRequired.php
index 21be7ac..9ab14af 100644
--- a/tests/Middleware/OptionalRequired.php
+++ b/tests/Middleware/OptionalRequired.php
@@ -6,14 +6,17 @@
 
 use Closure;
 use Illuminate\Http\Request;
+use const PHP_MAJOR_VERSION;
 use TiMacDonald\Middleware\HasParameters;
 
-class OptionalRequired
-{
-    use HasParameters;
-
-    public function handle(Request $request, Closure $next, string $optional = 'default', string $required): void
+if (PHP_MAJOR_VERSION < 8) {
+    class OptionalRequired
     {
-        //
+        use HasParameters;
+
+        public function handle(Request $request, Closure $next, string $optional, string $required): void
+        {
+            //
+        }
     }
 }