diff --git a/src/class_diagram/generators/plantuml/class_diagram_generator.cc b/src/class_diagram/generators/plantuml/class_diagram_generator.cc
index c41385cc..6961a439 100644
--- a/src/class_diagram/generators/plantuml/class_diagram_generator.cc
+++ b/src/class_diagram/generators/plantuml/class_diagram_generator.cc
@@ -107,10 +107,10 @@ void generator::generate_alias(const concept_ &c, std::ostream &ostr) const
     print_debug(c, ostr);
 
     if (m_config.generate_packages())
-        ostr << "annotation"
+        ostr << "class"
              << " \"" << c.name();
     else
-        ostr << "annotation"
+        ostr << "class"
              << " \"" << render_name(c.full_name());
 
     ostr << "\" as " << c.alias() << '\n';
@@ -300,7 +300,7 @@ void generator::generate(const concept_ &c, std::ostream &ostr) const
 {
     namespace plantuml_common = clanguml::common::generators::plantuml;
 
-    std::string class_type{"annotation"};
+    std::string class_type{"class"};
 
     ostr << class_type << " " << c.alias() << " <<concept>>";
 
diff --git a/src/class_diagram/visitor/translation_unit_visitor.cc b/src/class_diagram/visitor/translation_unit_visitor.cc
index 5bfc8bc0..14d4ff23 100644
--- a/src/class_diagram/visitor/translation_unit_visitor.cc
+++ b/src/class_diagram/visitor/translation_unit_visitor.cc
@@ -415,8 +415,6 @@ bool translation_unit_visitor::TraverseConceptDecl(clang::ConceptDecl *cpt)
 
         // process 'requires (...)' declaration
         for (const auto *decl : constraint->getBody()->decls()) {
-            // decl->dump();
-
             if (const auto *parm_var_decl =
                     clang::dyn_cast<clang::ParmVarDecl>(decl);
                 parm_var_decl) {
@@ -491,38 +489,92 @@ void translation_unit_visitor::find_relationships_in_constraint_expression(
     if (expr == nullptr)
         return;
 
-    if (const auto *concept_specialization =
-            clang::dyn_cast<clang::ConceptSpecializationExpr>(expr);
-        concept_specialization) {
-        if (concept_specialization->getNamedConcept() &&
-            diagram().should_include(concept_specialization->getNamedConcept()
-                                         ->getQualifiedNameAsString())) {
-            auto target_id = get_ast_local_id(
-                concept_specialization->getNamedConcept()->getID())
-                                 .value();
+    common::if_dyn_cast<clang::ConceptSpecializationExpr>(
+        expr, [&](const auto *cs) {
+            process_concept_specialization_relationships(c, cs);
+        });
 
-            for (const auto ta :
-                concept_specialization->getTemplateArguments()) {
-                if (ta.getKind() == clang::TemplateArgument::Template)
-                    ta.getAsTemplateOrTemplatePattern().dump();
-            }
-
-            c.add_relationship({relationship_t::kDependency, target_id});
-        }
-    }
-    else if (const auto *constraint =
-                 clang::dyn_cast<clang::RequiresExpr>(expr);
-             constraint) {
+    common::if_dyn_cast<clang::RequiresExpr>(expr, [&](const auto *re) {
         // TODO
-    }
-    else if (const auto *binop = clang::dyn_cast<clang::BinaryOperator>(expr);
-             binop) {
-        find_relationships_in_constraint_expression(c, binop->getLHS());
-        find_relationships_in_constraint_expression(c, binop->getRHS());
-    }
-    else if (const auto *unop = clang::dyn_cast<clang::UnaryOperator>(expr);
-             unop) {
-        find_relationships_in_constraint_expression(c, unop->getSubExpr());
+    });
+
+    common::if_dyn_cast<clang::BinaryOperator>(expr, [&](const auto *op) {
+        find_relationships_in_constraint_expression(c, op->getLHS());
+        find_relationships_in_constraint_expression(c, op->getRHS());
+    });
+
+    common::if_dyn_cast<clang::UnaryOperator>(expr, [&](const auto *op) {
+        find_relationships_in_constraint_expression(c, op->getSubExpr());
+    });
+}
+
+void translation_unit_visitor::process_concept_specialization_relationships(
+    common::model::element &c,
+    const clang::ConceptSpecializationExpr *concept_specialization)
+{
+    const auto *cpt = concept_specialization->getNamedConcept();
+    if (cpt && diagram().should_include(cpt->getQualifiedNameAsString())) {
+        auto target_id = get_ast_local_id(cpt->getID()).value();
+
+        std::vector<std::string> constrained_template_params;
+
+        size_t argument_index{};
+        for (const auto ta : concept_specialization->getTemplateArguments()) {
+
+            if (ta.getKind() == clang::TemplateArgument::Type) {
+                auto type_name =
+                    common::to_string(ta.getAsType(), cpt->getASTContext());
+
+                if (const auto *nested_template_type =
+                        ta.getAsType()->getAs<clang::TemplateTypeParmType>();
+                    nested_template_type != nullptr) {
+
+                    auto declaration_text = common::get_source_text_raw(
+                        concept_specialization->getSourceRange(),
+                        source_manager());
+
+                    if (!declaration_text.empty()) {
+                        // Handle typename constraint in requires clause
+                        if (type_name.find("type-parameter-") == 0) {
+                            declaration_text = declaration_text.substr(
+                                declaration_text.find(cpt->getNameAsString()) +
+                                cpt->getNameAsString().size() + 1);
+
+                            auto template_params =
+                                common::parse_unexposed_template_params(
+                                    declaration_text,
+                                    [](const auto &t) { return t; });
+
+                            if (template_params.size() > argument_index)
+                                type_name =
+                                    template_params[argument_index].to_string(
+                                        config().using_namespace(), false);
+                            else {
+                                LOG_DBG("Failed to find type specialization "
+                                        "for argument "
+                                        "{} at index {} in declaration "
+                                        "\n===\n{}\n===\n",
+                                    type_name, argument_index,
+                                    declaration_text);
+                            }
+                        }
+                        constrained_template_params.push_back(type_name);
+                    }
+                }
+            }
+            else {
+                auto type_name =
+                    common::to_string(ta.getAsType(), cpt->getASTContext());
+                LOG_DBG(
+                    "=== Unsupported concept type parameter: {}", type_name);
+            }
+            argument_index++;
+        }
+        if (!constrained_template_params.empty())
+            c.add_relationship(
+                {relationship_t::kDependency, target_id, access_t::kNone,
+                    fmt::format(
+                        "{}", fmt::join(constrained_template_params, ","))});
     }
 }
 
@@ -817,9 +869,19 @@ bool translation_unit_visitor::process_template_parameters(
                 util::apply_if_not_null(
                     template_type_parameter->getTypeConstraint()
                         ->getNamedConcept(),
-                    [&ct](const clang::ConceptDecl *named_concept) mutable {
+                    [this, &ct, &templated_element](
+                        const clang::ConceptDecl *named_concept) mutable {
                         ct.set_concept_constraint(
                             named_concept->getQualifiedNameAsString());
+                        if (templated_element &&
+                            diagram().should_include(
+                                named_concept->getQualifiedNameAsString())) {
+                            templated_element.value().add_relationship(
+                                {relationship_t::kDependency,
+                                    get_ast_local_id(named_concept->getID())
+                                        .value(),
+                                    access_t::kNone, ct.name()});
+                        }
                     });
             }
 
@@ -867,7 +929,7 @@ void translation_unit_visitor::process_template_record_containment(
 {
     assert(record.getParent()->isRecord());
 
-    const auto *parent = record.getParent(); //->getOuterLexicalRecordContext();
+    const auto *parent = record.getParent();
 
     if (parent != nullptr) {
         if (const auto *record_decl =
diff --git a/src/class_diagram/visitor/translation_unit_visitor.h b/src/class_diagram/visitor/translation_unit_visitor.h
index 2c8d65d7..7cd87153 100644
--- a/src/class_diagram/visitor/translation_unit_visitor.h
+++ b/src/class_diagram/visitor/translation_unit_visitor.h
@@ -293,5 +293,7 @@ private:
         std::tuple<std::string /* field name */, common::model::relationship_t,
             common::model::access_t>>
         anonymous_struct_relationships_;
+    void process_concept_specialization_relationships(common::model::element &c,
+        const clang::ConceptSpecializationExpr *concept_specialization);
 };
 } // namespace clanguml::class_diagram::visitor
diff --git a/src/common/clang_utils.h b/src/common/clang_utils.h
index 6b64ef0a..584e7af3 100644
--- a/src/common/clang_utils.h
+++ b/src/common/clang_utils.h
@@ -147,4 +147,16 @@ std::vector<common::model::template_parameter> parse_unexposed_template_params(
     const std::string &params,
     const std::function<std::string(const std::string &)> &ns_resolve,
     int depth = 0);
+
+template <typename T, typename P, typename F>
+void if_dyn_cast(P pointer, F &&func)
+{
+    if (pointer == nullptr)
+        return;
+
+    if (const auto *dyn_cast_value = clang::dyn_cast<T>(pointer);
+        dyn_cast_value) {
+        std::forward<F>(func)(dyn_cast_value);
+    }
+}
 } // namespace clanguml::common
diff --git a/src/common/model/enums.h b/src/common/model/enums.h
index e8c0779b..dd0ccea6 100644
--- a/src/common/model/enums.h
+++ b/src/common/model/enums.h
@@ -23,7 +23,7 @@ namespace clanguml::common::model {
 
 enum class diagram_t { kClass, kSequence, kPackage, kInclude };
 
-enum class access_t { kPublic, kProtected, kPrivate };
+enum class access_t { kPublic, kProtected, kPrivate, kNone };
 
 enum class relationship_t {
     kNone,
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 26f64965..224fc65b 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -18,7 +18,7 @@ endif(MSVC)
 list(FIND CMAKE_CXX_COMPILE_FEATURES cxx_std_20 SUPPORTS_CXX_STD_20)
 
 if(SUPPORTS_CXX_STD_20 EQUAL -1
-        OR ${LLVM_PACKAGE_VERSION} VERSION_LESS "15.0")
+        OR ${LLVM_PACKAGE_VERSION} VERSION_LESS "14.0")
     set(ENABLE_CXX_STD_20_TEST_CASES 0)
     foreach(CXX20_TC ${TEST_CASES_REQUIRING_CXX20})
         list(FILTER TEST_CASE_SOURCES
diff --git a/tests/t00056/t00056.cc b/tests/t00056/t00056.cc
index 088b114b..57af9f4e 100644
--- a/tests/t00056/t00056.cc
+++ b/tests/t00056/t00056.cc
@@ -4,10 +4,10 @@ namespace clanguml {
 namespace t00056 {
 
 template <typename T, typename L>
-concept greater_than = sizeof(T) > sizeof(L);
+concept greater_than_simple = sizeof(T) > sizeof(L);
 
 template <typename T, typename P>
-concept greater_than_requires = requires(T l, P r)
+concept greater_than_with_requires = requires(T l, P r)
 {
     sizeof(l) > sizeof(r);
 };
@@ -60,8 +60,8 @@ struct B {
     T b;
 };
 
-// Anonymous concept requirement
-template <typename T>
+// Anonymous concept requirement (TODO)
+template <convertible_to_string T>
 requires requires(T t)
 {
     --t;
@@ -71,5 +71,25 @@ struct C {
     T c;
 };
 
+template <iterable T1, typename T2, iterable T3, typename T4, typename T5>
+requires max_four_bytes<T2> && max_four_bytes<T5>
+struct D {
+};
+
+template <typename T1, typename T2, typename T3>
+requires greater_than_with_requires<T1, T3>
+struct E {
+    T1 e1;
+    T2 e2;
+    T3 e3;
+};
+
+template <typename T1, typename T2, typename T3>
+requires greater_than_simple<T1, T3>
+struct F {
+    T1 f1;
+    T2 f2;
+    T3 f3;
+};
 }
 }
\ No newline at end of file