diff --git a/external/tox_ngc_ft1/tox_ngc_ft1 b/external/tox_ngc_ft1/tox_ngc_ft1
index 27aeb03..c9f5e73 160000
--- a/external/tox_ngc_ft1/tox_ngc_ft1
+++ b/external/tox_ngc_ft1/tox_ngc_ft1
@@ -1 +1 @@
-Subproject commit 27aeb03a61d7fabb37b19272122fa38f7169fedf
+Subproject commit c9f5e73e4296339529ecb111e2a027478f6d7c9d
diff --git a/src/states/sha1.hpp b/src/states/sha1.hpp
index 616a3f1..2793716 100644
--- a/src/states/sha1.hpp
+++ b/src/states/sha1.hpp
@@ -9,6 +9,7 @@
 
 #include <unordered_map>
 #include <map>
+#include <optional>
 #include <vector>
 #include <deque>
 #include <random>
diff --git a/src/tox_callbacks.hpp b/src/tox_callbacks.hpp
index 9ad2958..dfd11e0 100644
--- a/src/tox_callbacks.hpp
+++ b/src/tox_callbacks.hpp
@@ -2,6 +2,8 @@
 
 #include <tox/tox.h>
 
+extern "C" {
+
 // logging
 void log_cb(Tox *tox, TOX_LOG_LEVEL level, const char *file, uint32_t line, const char *func, const char *message, void *user_data);
 
@@ -52,3 +54,5 @@ bool ft1_recv_init_sha1_chunk_cb(Tox *tox, uint32_t group_number, uint32_t peer_
 void ft1_recv_data_sha1_chunk_cb(Tox *tox, uint32_t group_number, uint32_t peer_number, uint8_t transfer_id, size_t data_offset, const uint8_t* data, size_t data_size, void* user_data);
 void ft1_send_data_sha1_chunk_cb(Tox *tox, uint32_t group_number, uint32_t peer_number, uint8_t transfer_id, size_t data_offset, uint8_t* data, size_t data_size, void* user_data);
 
+} // extern C
+