diff --git a/composer.json b/composer.json
index 602a473..e7230f4 100644
--- a/composer.json
+++ b/composer.json
@@ -13,10 +13,11 @@
     "require": {
         "php": "^7.4 || ^8.0",
         "php-stubs/wordpress-stubs": "^6.6.2",
-        "phpstan/phpstan": "^2.1.18"
+        "phpstan/phpstan": "^2.0"
     },
     "require-dev": {
         "composer/composer": "^2.1.14",
+        "composer/semver": "^3.4",
         "dealerdirect/phpcodesniffer-composer-installer": "^1.0",
         "php-parallel-lint/php-parallel-lint": "^1.1",
         "phpstan/phpstan-strict-rules": "^2.0",
@@ -42,7 +43,8 @@
     "config": {
         "allow-plugins": {
             "dealerdirect/phpcodesniffer-composer-installer": true
-        }
+        },
+        "sort-packages": true
     },
     "extra": {
         "phpstan": {
diff --git a/tests/DynamicReturnTypeExtensionTest.php b/tests/DynamicReturnTypeExtensionTest.php
index 4f3df6c..5f1c3bb 100644
--- a/tests/DynamicReturnTypeExtensionTest.php
+++ b/tests/DynamicReturnTypeExtensionTest.php
@@ -11,13 +11,19 @@ class DynamicReturnTypeExtensionTest extends \PHPStan\Testing\TypeInferenceTestC
      */
     public function dataFileAsserts(): iterable
     {
-        // Path to a file with actual asserts of expected types:
+        $phpstanVersion = self::getContainer()->getByType(InstalledPhpStanVersion::class);
+
+        if ($phpstanVersion->satisfies('^2.1.18')) {
+            // Improved rtrim handling in PHPStan 2.1.18 gives different results
+            yield from self::gatherAssertTypes(__DIR__ . '/data/slashit-functions.php');
+        }
+
+        // Include for all supported PHPStan versions
         yield from self::gatherAssertTypes(__DIR__ . '/data/apply-filters.php');
         yield from self::gatherAssertTypes(__DIR__ . '/data/ApplyFiltersTestClass.php');
         yield from self::gatherAssertTypes(__DIR__ . '/data/esc-sql.php');
         yield from self::gatherAssertTypes(__DIR__ . '/data/normalize-whitespace.php');
         yield from self::gatherAssertTypes(__DIR__ . '/data/shortcode-atts.php');
-        yield from self::gatherAssertTypes(__DIR__ . '/data/slashit-functions.php');
         yield from self::gatherAssertTypes(__DIR__ . '/data/stripslashes-from-strings-only.php');
         yield from self::gatherAssertTypes(__DIR__ . '/data/wp-parse-url.php');
         yield from self::gatherAssertTypes(__DIR__ . '/data/wp-slash.php');
@@ -34,6 +40,9 @@ public function testFileAsserts(string $assertType, string $file, ...$args): voi
 
     public static function getAdditionalConfigFiles(): array
     {
-        return [dirname(__DIR__) . '/vendor/szepeviktor/phpstan-wordpress/extension.neon'];
+        return [
+            dirname(__DIR__) . '/vendor/szepeviktor/phpstan-wordpress/extension.neon',
+            __DIR__ . '/test-services.neon',
+        ];
     }
 }
diff --git a/tests/InstalledPhpStanVersion.php b/tests/InstalledPhpStanVersion.php
new file mode 100644
index 0000000..90b4eae
--- /dev/null
+++ b/tests/InstalledPhpStanVersion.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SzepeViktor\PHPStan\WordPress\Tests;
+
+use Composer\InstalledVersions;
+use Composer\Semver\Semver;
+
+final class InstalledPhpStanVersion
+{
+    private string $version;
+
+    public function __construct()
+    {
+        $version = InstalledVersions::getVersion('phpstan/phpstan-src');
+
+        if ($version === null) {
+            throw new \RuntimeException('Cannot determine PHPStan version from Composer.');
+        }
+
+        $this->version = $version;
+    }
+
+    public function satisfies(string $constraints): bool
+    {
+        return Semver::satisfies($this->version, $constraints);
+    }
+}
diff --git a/tests/test-services.neon b/tests/test-services.neon
new file mode 100644
index 0000000..e453d3b
--- /dev/null
+++ b/tests/test-services.neon
@@ -0,0 +1,3 @@
+services:
+    -
+        class: SzepeViktor\PHPStan\WordPress\Tests\InstalledPhpStanVersion