diff --git a/NOTES.txt b/NOTES.txt
index 9766179c5..cbbc977d0 100644
--- a/NOTES.txt
+++ b/NOTES.txt
@@ -1044,3 +1044,31 @@ Compilation time and Memory usage:
 MSVC2019          9.9GB 1:27
 MSVC2022          8.0GB 1:25
 clang-cl MSVC2022 5.5GB 1:35
+
+
+bugs:
+-----
+
+- BUG std::unordered_map can not be instantiated with the incomplete value type, reproducible only on the Linux GCC/Clang, MSYS2 and msvc don't have any problem with the incomplete type ✨🚀
+
+add this to the testforplay.cpp
+
+#include <filesystem>
+#include <iostream>
+#include <typeindex>
+#include <typeinfo>
+
+#include <unordered_map>
+
+namespace Models {
+class Torrent;
+}
+
+struct Test1
+{
+    std::unordered_map<QString, Models::Torrent> m_a {};
+};
+
+#include <range/v3/all.hpp>
+
+#include <orm/db.hpp>
diff --git a/include/orm/tiny/concerns/hasrelationships.hpp b/include/orm/tiny/concerns/hasrelationships.hpp
index 9b600a9de..eb8d4f2a5 100644
--- a/include/orm/tiny/concerns/hasrelationships.hpp
+++ b/include/orm/tiny/concerns/hasrelationships.hpp
@@ -225,7 +225,7 @@ namespace Concerns
         /*! Map of relation names to methods. */
         QHash<QString, RelationVisitor> u_relations;
 
-        // BUG std::unordered_map prevents to compile on GCC, if I comment out std::optional<AllRelations>... in the RelationsType<AllRelations...>, or I change it to the QHash, then it compile, I'm absolutelly lost why this is happening 😞😭, I can't change to the QHash because of 25734deb, I have created simple test project gcc_trivial_bug_test in merydeye-gentoo, but std::map works so it is a big win, because now I can compile whole project on gcc ✨🚀 silverqx
+        // BUG std::unordered_map can not be instantiated with the incomplete value type, reproducible only on the Linux GCC/Clang, MSYS2 and msvc don't have any problem with the incomplete type ✨🚀 ; added section to the NOTES.txt how to reproduce ; OLD - std::unordered_map prevents to compile on GCC, if I comment out std::optional<AllRelations>... in the RelationsType<AllRelations...>, or I change it to the QHash, then it compile, I'm absolutelly lost why this is happening 😞😭, I can't change to the QHash because of 25734deb, I have created simple test project gcc_trivial_bug_test in merydeye-gentoo, but std::map works so it is a big win, because now I can compile whole project on gcc silverqx
         /*! The loaded relationships for the model. */
 #ifdef __GNUG__
         std::map<QString, RelationsType<AllRelations...>> m_relations;