diff --git a/src/3rdparty/CMakeLists.txt b/src/3rdparty/CMakeLists.txt
index 29ace8dc50..293fbaa7d4 100644
--- a/src/3rdparty/CMakeLists.txt
+++ b/src/3rdparty/CMakeLists.txt
@@ -6,3 +6,5 @@ add_subdirectory(cpp-btree)
 add_subdirectory(mingw-std-threads)
 add_subdirectory(monocypher)
 add_subdirectory(randombytes)
+add_subdirectory(optional)
+add_subdirectory(robin_hood)
diff --git a/src/3rdparty/optional/CMakeLists.txt b/src/3rdparty/optional/CMakeLists.txt
new file mode 100644
index 0000000000..f529dcd1ee
--- /dev/null
+++ b/src/3rdparty/optional/CMakeLists.txt
@@ -0,0 +1,4 @@
+add_files(
+    optional.hpp
+    ottd_optional.h
+)