diff --git a/bin/composer-dependency-analyser b/bin/composer-dependency-analyser
index 5750e5a..16307bd 100755
--- a/bin/composer-dependency-analyser
+++ b/bin/composer-dependency-analyser
@@ -93,7 +93,7 @@ try {
 }
 
 // load vendor that belongs to given composer.json
-$autoloadFile = dirname($composerJsonPath) . '/' . $composerJson->vendorDir . '/autoload.php';
+$autoloadFile = $composerJson->composerAutoloadPath;
 if (is_file($autoloadFile)) {
     require_once $autoloadFile;
 } else {
diff --git a/src/ComposerJson.php b/src/ComposerJson.php
index fc6406e..bac8fb8 100644
--- a/src/ComposerJson.php
+++ b/src/ComposerJson.php
@@ -19,6 +19,7 @@
 use function json_last_error;
 use function json_last_error_msg;
 use function realpath;
+use function rtrim;
 use function strpos;
 use const ARRAY_FILTER_USE_KEY;
 use const JSON_ERROR_NONE;
@@ -30,7 +31,7 @@ class ComposerJson
      * @readonly
      * @var string
      */
-    public $vendorDir;
+    public $composerAutoloadPath;
 
     /**
      * Package => isDev
@@ -57,7 +58,7 @@ public function __construct(string $composerJsonPath)
         $basePath = dirname($composerJsonPath);
 
         $composerJsonData = $this->parseComposerJson($composerJsonPath);
-        $this->vendorDir = $composerJsonData['vendor-dir'] ?? 'vendor';
+        $this->composerAutoloadPath = $this->resolveComposerAutoloadPath($basePath, $composerJsonData['config']['vendor-dir'] ?? 'vendor');
 
         $requiredPackages = $composerJsonData['require'] ?? [];
         $requiredDevPackages = $composerJsonData['require-dev'] ?? [];
@@ -147,7 +148,9 @@ private function realpath(string $path): string
      * @return array{
      *     require?: array<string, string>,
      *     require-dev?: array<string, string>,
-     *     vendor-dir?: string,
+     *     config?: array{
+     *         vendor-dir?: string,
+     *     },
      *     autoload?: array{
      *          psr-0?: array<string, string|string[]>,
      *          psr-4?: array<string, string|string[]>,
@@ -186,4 +189,15 @@ private function parseComposerJson(string $composerJsonPath): array
         return $composerJsonData; // @phpstan-ignore-line ignore mixed returned
     }
 
+    private function resolveComposerAutoloadPath(string $basePath, string $vendorDir): string
+    {
+        $vendorDir = rtrim($vendorDir, '/');
+
+        if (is_dir($vendorDir)) {
+            return $vendorDir . '/autoload.php';
+        }
+
+        return $basePath . '/' . $vendorDir . '/autoload.php';
+    }
+
 }
diff --git a/tests/ComposerJsonTest.php b/tests/ComposerJsonTest.php
index abff308..b0c5f0d 100644
--- a/tests/ComposerJsonTest.php
+++ b/tests/ComposerJsonTest.php
@@ -3,14 +3,24 @@
 namespace ShipMonk\ComposerDependencyAnalyser;
 
 use PHPUnit\Framework\TestCase;
+use function dirname;
+use function file_put_contents;
+use function json_encode;
 use function realpath;
+use function sys_get_temp_dir;
 
 class ComposerJsonTest extends TestCase
 {
 
     public function testComposerJson(): void
     {
-        $composerJson = new ComposerJson(__DIR__ . '/data/not-autoloaded/composer/sample.json');
+        $composerJsonPath = __DIR__ . '/data/not-autoloaded/composer/sample.json';
+        $composerJson = new ComposerJson($composerJsonPath);
+
+        self::assertSame(
+            dirname($composerJsonPath) . '/custom-vendor/autoload.php',
+            $composerJson->composerAutoloadPath
+        );
 
         self::assertSame(
             [
@@ -30,4 +40,24 @@ public function testComposerJson(): void
         );
     }
 
+    public function testAbsoluteCustomVendorDir(): void
+    {
+        $generatedComposerJson = sys_get_temp_dir() . '/custom-vendor.json';
+        file_put_contents($generatedComposerJson, json_encode([
+            'require' => [
+                'nette/utils' => '^3.0',
+            ],
+            'config' => [
+                'vendor-dir' => sys_get_temp_dir(),
+            ],
+        ]));
+
+        $composerJson = new ComposerJson($generatedComposerJson);
+
+        self::assertSame(
+            sys_get_temp_dir() . '/autoload.php',
+            $composerJson->composerAutoloadPath
+        );
+    }
+
 }
diff --git a/tests/data/not-autoloaded/composer/sample.json b/tests/data/not-autoloaded/composer/sample.json
index 6e6ffb1..7cf5ac1 100644
--- a/tests/data/not-autoloaded/composer/sample.json
+++ b/tests/data/not-autoloaded/composer/sample.json
@@ -13,5 +13,8 @@
         "files": [
             "dir2/file1.php"
         ]
+    },
+    "config": {
+        "vendor-dir": "custom-vendor/"
     }
 }