diff --git a/src/__stl__.h b/src/__stl__.h
index b7cb8e4c..f11ce5a7 100644
--- a/src/__stl__.h
+++ b/src/__stl__.h
@@ -17,7 +17,7 @@
 #include <queue>
 #include <iomanip>
 #include <map>
-#include <utility>
+#include <optional>
 
 #include <thread>
 #include <atomic>