diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 3c77bd4..0b2540c 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -5,7 +5,7 @@ includes:
     - vendor/phpstan/phpstan-phpunit/rules.neon
 
 parameters:
-    level: 4
+    level: 5
 
     paths:
         - config
@@ -25,6 +25,10 @@ parameters:
             - tests/Checks/PackageSecurityHealthCheckTest.php
             - tests/Stubs/Checks/PackageSecurityHealthCheck.php
 
+        - message: '#(?:C|c)lass SensioLabs\\Security\\SecurityChecker not found#'
+          paths:
+            - src/Checks/PackageSecurityHealthCheck.php
+
         - message: '#Call to method .+ on an unknown class Enlightn\\SecurityChecker\\SecurityChecker#'
           paths:
             - src/Checks/PackageSecurityHealthCheck.php
diff --git a/src/AppHealth.php b/src/AppHealth.php
index e55d2d0..bfce1e7 100644
--- a/src/AppHealth.php
+++ b/src/AppHealth.php
@@ -10,7 +10,7 @@ class AppHealth
 {
     public function __construct(
         /**
-         * @var Collection<int, HealthCheck>
+         * @var Collection<int, covariant HealthCheck>
          */
         protected Collection $checks,
     ) {
@@ -40,7 +40,7 @@ public function fails($checkName): bool
     /**
      * Returns a collection of all health checks
      *
-     * @return Collection<int, HealthCheck>
+     * @return Collection<int, covariant HealthCheck>
      */
     public function all(): Collection
     {
diff --git a/src/Checks/HttpHealthCheck.php b/src/Checks/HttpHealthCheck.php
index 79f15db..07ae9c6 100644
--- a/src/Checks/HttpHealthCheck.php
+++ b/src/Checks/HttpHealthCheck.php
@@ -34,7 +34,7 @@ public function status(): Status
         $badConnections = collect();
 
         /**
-         * @var Collection<string, string> $generalFailures
+         * @var Collection<string, array<string|int|array>> $generalFailures
          */
         $generalFailures = collect();
 
@@ -80,7 +80,7 @@ public function status(): Status
     /**
      * @param Collection<string, array<string, string>> $badResponses
      * @param Collection<string, string> $badConnections
-     * @param Collection<string, string> $generalFailures
+     * @param Collection<string, array<string|int|array>> $generalFailures
      */
     private function isOkay(Collection $badResponses, Collection $badConnections, Collection $generalFailures): bool
     {
diff --git a/src/Checks/PackageSecurityHealthCheck.php b/src/Checks/PackageSecurityHealthCheck.php
index ce21090..cfc56aa 100644
--- a/src/Checks/PackageSecurityHealthCheck.php
+++ b/src/Checks/PackageSecurityHealthCheck.php
@@ -34,7 +34,7 @@ public function status(): Status
     {
         try {
             if (! static::checkDependency(SecurityChecker::class)) {
-                if (static::checkDependency('SensioLabs\Security\SecurityChecker')) {
+                if (static::checkDependency(\SensioLabs\Security\SecurityChecker::class)) {
                     throw new Exception(
                         'The sensiolabs/security-checker package has been archived.'
                             . ' Install enlightn/security-checker instead.'
diff --git a/tests/Checks/CrossServiceHealthCheckTest.php b/tests/Checks/CrossServiceHealthCheckTest.php
index c305eb8..4079b7b 100644
--- a/tests/Checks/CrossServiceHealthCheckTest.php
+++ b/tests/Checks/CrossServiceHealthCheckTest.php
@@ -53,7 +53,7 @@ public function testSkipsCheckIfXServiceCheckHeaderIsPresent(): void
         $container = [];
         $client = $this->mockClient(new Response(500), $container);
         $request = Request::create('/');
-        $request->headers->set('X-Service-Check', true);
+        $request->headers->set('X-Service-Check', 'true');
 
         $check = new CrossServiceHealthCheck($client, $request);
 
diff --git a/tests/Checks/FtpHealthCheckTest.php b/tests/Checks/FtpHealthCheckTest.php
index 9b09cd2..674075e 100644
--- a/tests/Checks/FtpHealthCheckTest.php
+++ b/tests/Checks/FtpHealthCheckTest.php
@@ -12,10 +12,9 @@ class FtpHealthCheckTest extends TestCase
 {
     public function testShowsProblemWhenCantConnectToFtpServer(): void
     {
-        $ftp = Mockery::mock(FtpAdapter::class)
-            ->expects('listContents')
-            ->andThrow(new  UnableToConnectToFtpHost('uwu'))
-            ->getMock();
+        $ftp = Mockery::mock(FtpAdapter::class);
+        $ftp->expects('listContents')
+            ->andThrow(new  UnableToConnectToFtpHost('uwu'));
 
         $status = (new FtpHealthCheck($ftp))->status();
 
@@ -32,8 +31,8 @@ public function testShowsOkayWhenCanConnectToFtpServer(): void
             yield 'baz';
         };
 
-        $ftp = Mockery::mock(FtpAdapter::class)
-            ->expects('listContents')
+        $ftp = Mockery::mock(FtpAdapter::class);
+        $ftp->expects('listContents')
             ->andReturn($generator())
             ->getMock();