diff --git a/core/sched/thread_pool.hpp b/core/sched/thread_pool.hpp
index ed6d304..de8731a 100644
--- a/core/sched/thread_pool.hpp
+++ b/core/sched/thread_pool.hpp
@@ -19,6 +19,7 @@
 #include <mutex>
 #include <condition_variable>
 #include <exception>
+#include <optional>
 
 namespace Maike::Sched
 {