diff --git a/backends/llamacpp/csrc/ffi.hpp b/backends/llamacpp/csrc/ffi.hpp
index f33a2f1a..a3d14ee5 100644
--- a/backends/llamacpp/csrc/ffi.hpp
+++ b/backends/llamacpp/csrc/ffi.hpp
@@ -8,6 +8,7 @@
 #include <exception>
 #include <filesystem>
 #include <string_view>
+#include <variant>
 
 #include <spdlog/spdlog.h>
 #include "backend.hpp"