diff --git a/library/DataIdentity.cpp b/library/DataIdentity.cpp
index 0a797c2069..111166d90e 100644
--- a/library/DataIdentity.cpp
+++ b/library/DataIdentity.cpp
@@ -65,6 +65,7 @@ namespace df {
     OPAQUE_IDENTITY_TRAITS(std::optional<std::function<void()> >);
     OPAQUE_IDENTITY_TRAITS(std::variant<std::string, std::function<void()> >);
     OPAQUE_IDENTITY_TRAITS(std::weak_ptr<df::widget_container>);
+    OPAQUE_IDENTITY_TRAITS(std::filesystem::file_time_type);
     OPAQUE_IDENTITY_TRAITS(wchar_t*);
 
     const buffer_container_identity buffer_container_identity::base_instance;
diff --git a/library/include/DataIdentity.h b/library/include/DataIdentity.h
index cf486e6188..c48dd299fd 100644
--- a/library/include/DataIdentity.h
+++ b/library/include/DataIdentity.h
@@ -632,6 +632,7 @@ namespace df
     OPAQUE_IDENTITY_TRAITS(std::optional<std::function<void()> >);
     OPAQUE_IDENTITY_TRAITS(std::variant<std::string, std::function<void()> >);
     OPAQUE_IDENTITY_TRAITS(std::weak_ptr<df::widget_container>);
+    OPAQUE_IDENTITY_TRAITS(std::filesystem::file_time_type);
 
 #ifdef BUILD_DFHACK_LIB
     template<typename T>