diff --git a/src/class_diagram/generators/plantuml/class_diagram_generator.cc b/src/class_diagram/generators/plantuml/class_diagram_generator.cc
index 68af5b36..0f8ae605 100644
--- a/src/class_diagram/generators/plantuml/class_diagram_generator.cc
+++ b/src/class_diagram/generators/plantuml/class_diagram_generator.cc
@@ -52,6 +52,13 @@ void generator::generate_link(
     ostr << "]]]";
 }
 
+std::string generator::render_name(std::string name) const
+{
+    util::replace_all(name, "##", "::");
+
+    return name;
+}
+
 void generator::generate_alias(const class_ &c, std::ostream &ostr) const
 {
     std::string class_type{"class"};
@@ -64,10 +71,9 @@ void generator::generate_alias(const class_ &c, std::ostream &ostr) const
     else
         full_name = c.full_name();
 
-    if (full_name.empty())
-        full_name = "<<anonymous>>";
+    assert(!full_name.empty());
 
-    ostr << class_type << " \"" << full_name;
+    ostr << class_type << " \"" << render_name(full_name);
 
     ostr << "\" as " << c.alias() << '\n';
 
@@ -82,7 +88,7 @@ void generator::generate_alias(const enum_ &e, std::ostream &ostr) const
              << " \"" << e.name();
     else
         ostr << "enum"
-             << " \"" << e.full_name();
+             << " \"" << render_name(e.full_name());
 
     ostr << "\" as " << e.alias() << '\n';
 
@@ -225,7 +231,7 @@ void generator::generate(const class_ &c, std::ostream &ostr) const
             ostr << "{static} ";
 
         ostr << plantuml_common::to_plantuml(m.access()) << m.name() << " : "
-             << uns.relative(m.type());
+             << render_name(uns.relative(m.type()));
 
         if (m_config.generate_links) {
             generate_link(ostr, m);
diff --git a/src/class_diagram/generators/plantuml/class_diagram_generator.h b/src/class_diagram/generators/plantuml/class_diagram_generator.h
index a5b2a1a6..1c774019 100644
--- a/src/class_diagram/generators/plantuml/class_diagram_generator.h
+++ b/src/class_diagram/generators/plantuml/class_diagram_generator.h
@@ -76,6 +76,9 @@ public:
     void generate_relationships(const package &p, std::ostream &ostr) const;
 
     void generate(std::ostream &ostr) const override;
+
+private:
+    std::string render_name(std::string name) const;
 };
 
 }
diff --git a/src/class_diagram/visitor/translation_unit_visitor.cc b/src/class_diagram/visitor/translation_unit_visitor.cc
index 1f3d4c15..da30df25 100644
--- a/src/class_diagram/visitor/translation_unit_visitor.cc
+++ b/src/class_diagram/visitor/translation_unit_visitor.cc
@@ -146,7 +146,8 @@ bool translation_unit_visitor::VisitEnumDecl(clang::EnumDecl *enm)
     std::string qualified_name = common::get_qualified_name(*enm);
     namespace_ ns{qualified_name};
     ns.pop_back();
-    e.set_name(enm->getNameAsString());
+
+    e.set_name(common::get_tag_name(*enm));
     e.set_namespace(ns);
     e.set_id(common::to_id(*enm));
     set_ast_local_id(enm->getID(), e.id());
@@ -358,7 +359,7 @@ bool translation_unit_visitor::VisitCXXRecordDecl(clang::CXXRecordDecl *cls)
         forward_declarations_.erase(id);
 
     if (diagram_.should_include(class_model)) {
-        LOG_DBG("Adding class {} with id {}", class_model.full_name(),
+        LOG_DBG("Adding class {} with id {}", class_model.full_name(false),
             class_model.id());
 
         diagram_.add_class(std::move(c_ptr));
@@ -387,7 +388,8 @@ std::unique_ptr<class_> translation_unit_visitor::create_class_declaration(
 
     namespace_ ns{qualified_name};
     ns.pop_back();
-    c.set_name(cls->getNameAsString());
+
+    c.set_name(common::get_tag_name(*cls));
     c.set_namespace(ns);
     c.set_id(common::to_id(*cls));
 
@@ -415,6 +417,7 @@ void translation_unit_visitor::process_class_declaration(
 
     if (cls.getParent()->isRecord()) {
         process_record_containment(cls, c);
+        c.nested(true);
     }
 
     c.complete(true);
@@ -1809,10 +1812,6 @@ void translation_unit_visitor::process_field(
         common::to_string(field_type, field_declaration.getASTContext());
     // The field name
     const auto field_name = field_declaration.getNameAsString();
-    // If for any reason clang reports the type as empty string, make sure
-    // it has some default name
-    if (type_name.empty())
-        type_name = "<<anonymous>>";
 
     class_member field{
         detail::access_specifier_to_access_t(field_declaration.getAccess()),
diff --git a/src/common/clang_utils.cc b/src/common/clang_utils.cc
index 90ef71c1..5297cb1a 100644
--- a/src/common/clang_utils.cc
+++ b/src/common/clang_utils.cc
@@ -39,6 +39,35 @@ std::optional<clanguml::common::model::namespace_> get_enclosing_namespace(
         common::get_qualified_name(*namespace_declaration)};
 }
 
+std::string get_tag_name(const clang::TagDecl &declaration)
+{
+    auto base_name = declaration.getNameAsString();
+    if (base_name.empty()) {
+        base_name =
+            fmt::format("(anonymous_{})", std::to_string(declaration.getID()));
+    }
+
+    if (declaration.getParent() && declaration.getParent()->isRecord()) {
+        // If the record is nested within another record (e.g. class or struct)
+        // we have to maintain a containment namespace in order to ensure
+        // unique names within the diagram
+        std::deque<std::string> record_parent_names;
+        record_parent_names.push_front(base_name);
+
+        auto *cls_parent{declaration.getParent()};
+        while (cls_parent->isRecord()) {
+            auto parent_name =
+                static_cast<const clang::RecordDecl *>(cls_parent)
+                    ->getNameAsString();
+            record_parent_names.push_front(parent_name);
+            cls_parent = cls_parent->getParent();
+        }
+        return fmt::format("{}", fmt::join(record_parent_names, "##"));
+    }
+
+    return base_name;
+}
+
 std::string to_string(const clang::QualType &type, const clang::ASTContext &ctx,
     bool try_canonical)
 {
@@ -66,6 +95,14 @@ std::string to_string(const clang::QualType &type, const clang::ASTContext &ctx,
         }
     }
 
+    // If for any reason clang reports the type as empty string, make sure
+    // it has some default name
+    if (result.empty())
+        result = "(anonymous)";
+    else if (util::contains(result, "unnamed struct")) {
+        result = common::get_tag_name(*type->getAsTagDecl());
+    }
+
     // Remove trailing spaces after commas in template arguments
     clanguml::util::replace_all(result, ", ", ",");
 
diff --git a/src/common/clang_utils.h b/src/common/clang_utils.h
index 0395219c..1e1da03e 100644
--- a/src/common/clang_utils.h
+++ b/src/common/clang_utils.h
@@ -22,6 +22,7 @@
 
 #include <clang/AST/RecursiveASTVisitor.h>
 
+#include <deque>
 #include <filesystem>
 #include <string>
 
@@ -30,12 +31,23 @@ class NamespaceDecl;
 }
 
 namespace clanguml::common {
+std::string get_tag_name(const clang::TagDecl &declaration);
 
 template <typename T> std::string get_qualified_name(const T &declaration)
 {
     auto qualified_name = declaration.getQualifiedNameAsString();
     util::replace_all(qualified_name, "(anonymous namespace)", "");
     util::replace_all(qualified_name, "::::", "::");
+
+    if constexpr (std::is_base_of_v<clang::TagDecl, T>) {
+        auto base_name = get_tag_name(declaration);
+        model::namespace_ ns{qualified_name};
+        ns.pop_back();
+        ns = ns | base_name;
+
+        return ns.to_string();
+    }
+
     return qualified_name;
 }
 
diff --git a/src/common/model/diagram_element.cc b/src/common/model/diagram_element.cc
index e7bee8e2..5199c01b 100644
--- a/src/common/model/diagram_element.cc
+++ b/src/common/model/diagram_element.cc
@@ -28,6 +28,7 @@ std::atomic_uint64_t diagram_element::m_nextId = 1;
 
 diagram_element::diagram_element()
     : id_{0}
+    , nested_{false}
     , complete_{false}
 {
 }
@@ -84,6 +85,10 @@ inja::json diagram_element::context() const
     return ctx;
 }
 
+bool diagram_element::is_nested() const { return nested_; }
+
+void diagram_element::nested(bool nested) { nested_ = nested; }
+
 bool diagram_element::complete() const { return complete_; }
 
 void diagram_element::complete(bool completed) { complete_ = completed; }
diff --git a/src/common/model/diagram_element.h b/src/common/model/diagram_element.h
index 69753dbb..2d58bb62 100644
--- a/src/common/model/diagram_element.h
+++ b/src/common/model/diagram_element.h
@@ -65,6 +65,10 @@ public:
 
     virtual inja::json context() const;
 
+    bool is_nested() const;
+
+    void nested(bool nested);
+
     bool complete() const;
 
     void complete(bool completed);
@@ -73,7 +77,7 @@ private:
     id_t id_;
     std::string name_;
     std::vector<relationship> relationships_;
-
+    bool nested_;
     bool complete_;
 
     static std::atomic_uint64_t m_nextId;
diff --git a/tests/t00004/t00004.cc b/tests/t00004/t00004.cc
index 3216ba7a..d2f0a128 100644
--- a/tests/t00004/t00004.cc
+++ b/tests/t00004/t00004.cc
@@ -1,6 +1,11 @@
 namespace clanguml {
 namespace t00004 {
 
+class B {
+public:
+    enum AA { AA_1, AA_2, AA_3 };
+};
+
 class A {
 public:
     void foo() const { }
@@ -15,5 +20,6 @@ public:
 
     void foo2() const { }
 };
+
 }
 }
diff --git a/tests/t00004/test_case.h b/tests/t00004/test_case.h
index 4433098a..d0dd351f 100644
--- a/tests/t00004/test_case.h
+++ b/tests/t00004/test_case.h
@@ -41,12 +41,14 @@ TEST_CASE("t00004", "[test-case][class]")
     REQUIRE_THAT(puml, StartsWith("@startuml"));
     REQUIRE_THAT(puml, EndsWith("@enduml\n"));
     REQUIRE_THAT(puml, IsClass(_A("A")));
-    REQUIRE_THAT(puml, IsClass(_A("AA")));
-    REQUIRE_THAT(puml, IsClass(_A("AAA")));
-    REQUIRE_THAT(puml, IsEnum(_A("Lights")));
-    REQUIRE_THAT(puml, IsInnerClass(_A("A"), _A("AA")));
-    REQUIRE_THAT(puml, IsInnerClass(_A("AA"), _A("AAA")));
-    REQUIRE_THAT(puml, IsInnerClass(_A("AA"), _A("Lights")));
+    REQUIRE_THAT(puml, IsClass(_A("A::AA")));
+    REQUIRE_THAT(puml, IsClass(_A("A::AA::AAA")));
+    REQUIRE_THAT(puml, IsEnum(_A("B::AA")));
+    REQUIRE_THAT(puml, IsEnum(_A("A::AA::Lights")));
+    REQUIRE_THAT(puml, IsInnerClass(_A("A"), _A("A::AA")));
+    REQUIRE_THAT(puml, IsInnerClass(_A("A::AA"), _A("A::AA::AAA")));
+    REQUIRE_THAT(puml, IsInnerClass(_A("A::AA"), _A("A::AA::Lights")));
+
     REQUIRE_THAT(puml, (IsMethod<Public, Const>("foo")));
     REQUIRE_THAT(puml, (IsMethod<Public, Const>("foo2")));
 
diff --git a/tests/t00037/t00037.cc b/tests/t00037/t00037.cc
index c2b53adb..2d17af61 100644
--- a/tests/t00037/t00037.cc
+++ b/tests/t00037/t00037.cc
@@ -8,6 +8,11 @@ struct ST {
         double y;
         double z;
     } dimensions;
+
+    struct {
+        double c;
+        double h;
+    } units;
 };
 
 struct A {
@@ -17,6 +22,9 @@ struct A {
         st.dimensions.x = 1;
         st.dimensions.y = 1;
         st.dimensions.z = 1;
+
+        st.units.c = 1;
+        st.units.h = 1;
     }
 
     ST st;
diff --git a/tests/t00037/test_case.h b/tests/t00037/test_case.h
index f722aac2..06bf6435 100644
--- a/tests/t00037/test_case.h
+++ b/tests/t00037/test_case.h
@@ -37,7 +37,7 @@ TEST_CASE("t00037", "[test-case][class]")
 
     REQUIRE_THAT(puml, IsClass(_A("ST")));
     REQUIRE_THAT(puml, IsClass(_A("A")));
-    REQUIRE_THAT(puml, IsInnerClass(_A("ST"), _A("<<anonymous>>")));
+    REQUIRE_THAT(puml, IsClass(_A("ST::\\(anonymous_\\d+\\)")));
 
     save_puml(
         "./" + config.output_directory() + "/" + diagram->name + ".puml", puml);