diff --git a/src/ComposerJson.php b/src/ComposerJson.php
index 6280556..4e1d48f 100644
--- a/src/ComposerJson.php
+++ b/src/ComposerJson.php
@@ -128,7 +128,11 @@ private function extractAutoloadPaths(string $basePath, array $autoload, bool $i
             }
 
             foreach ($paths as $path) {
-                $absolutePath = $basePath . '/' . $path;
+                if (Path::isAbsolute($path)) {
+                    $absolutePath = $path;
+                } else {
+                    $absolutePath = $basePath . '/' . $path;
+                }
 
                 if (strpos($path, '*') !== false) { // https://getcomposer.org/doc/04-schema.md#classmap
                     $globPaths = glob($absolutePath);
diff --git a/tests/ComposerJsonTest.php b/tests/ComposerJsonTest.php
index 96bf1b4..401e0c0 100644
--- a/tests/ComposerJsonTest.php
+++ b/tests/ComposerJsonTest.php
@@ -41,6 +41,7 @@ public function testComposerJson(): void
                 realpath(__DIR__ . '/data/not-autoloaded/composer/dir2/file1.php') => false,
                 realpath(__DIR__ . '/data/not-autoloaded/composer/dir1') => false,
                 realpath(__DIR__ . '/data/not-autoloaded/composer/dir2') => false,
+                DIRECTORY_SEPARATOR . 'absolute' . DIRECTORY_SEPARATOR . 'dir' => false,
             ],
             $composerJson->autoloadPaths
         );
diff --git a/tests/data/not-autoloaded/composer/sample.json b/tests/data/not-autoloaded/composer/sample.json
index 56a307f..ef9ce40 100644
--- a/tests/data/not-autoloaded/composer/sample.json
+++ b/tests/data/not-autoloaded/composer/sample.json
@@ -8,7 +8,8 @@
     },
     "autoload": {
         "classmap": [
-            "dir*"
+            "dir*",
+            "/absolute/dir"
         ],
         "files": [
             "dir2/file1.php"