diff --git a/src/Runtime/Runtime.php b/src/Runtime/Runtime.php
index 571aebd..f0f30bb 100644
--- a/src/Runtime/Runtime.php
+++ b/src/Runtime/Runtime.php
@@ -471,6 +471,11 @@ class Runtime
      */
     public function getCurrentUser(): string
     {
+        // Windows fallback
+        if (!function_exists('posix_getpwuid')) {
+            return getenv('USERNAME') ?: '';
+        }
+
         $userData = posix_getpwuid(posix_geteuid());
         return $userData['name'];
     }