diff --git a/thirdparty/hnswlib/hnswlib/hnswlib.h b/thirdparty/hnswlib/hnswlib/hnswlib.h
index 4da2b70af..482f15459 100644
--- a/thirdparty/hnswlib/hnswlib/hnswlib.h
+++ b/thirdparty/hnswlib/hnswlib/hnswlib.h
@@ -129,6 +129,7 @@ AVX512Capable() {
 
 #include <fstream>
 #include <iostream>
+#include <optional>
 #include <queue>
 #include <vector>