diff --git a/qt6-after/qt6-migrated-legatus/Lts/DDS/Core/topic_lock_master.cpp b/qt6-after/qt6-migrated-legatus/Lts/DDS/Core/topic_lock_master.cpp
index 47d983978..b72a35aad 100755
--- a/qt6-after/qt6-migrated-legatus/Lts/DDS/Core/topic_lock_master.cpp
+++ b/qt6-after/qt6-migrated-legatus/Lts/DDS/Core/topic_lock_master.cpp
@@ -28,13 +28,13 @@ bool TopicLockMaster::init(const std::shared_ptr<DDSConnector::DdsConnector> &dd
   m_coreDtc->enableAll();
 
   m_coreDtc->lockedEntitys([this] (const LockedEntity &data) {
-    m_lockedEntitys << key(data.entityId(), data.exerciseId(), QString::fromStdString(data.entityTypeName()));
+    m_lockedEntitys << key(data.entityId, data.exerciseId, QString::fromStdString(data.entityTypeName));
   });
 
   connect(m_coreDtc.get(), &Interface::Dtc::lockedEntityChanged, this,
           [this] (const LockedEntity &data, DataModification modType)
           {
-            key k(data.entityId(), data.exerciseId(), QString::fromStdString(data.entityTypeName()));
+            key k(data.entityId, data.exerciseId, QString::fromStdString(data.entityTypeName));
             if (modType == DataModification::eAdded)
               m_lockedEntitys << k;
             else if (modType == DataModification::eRemoved)
diff --git a/qt6-after/qt6-migrated-legatus/Lts/DDS/Core/topic_lock_master.h b/qt6-after/qt6-migrated-legatus/Lts/DDS/Core/topic_lock_master.h
index fe83de7e1..b0cf455e4 100755
--- a/qt6-after/qt6-migrated-legatus/Lts/DDS/Core/topic_lock_master.h
+++ b/qt6-after/qt6-migrated-legatus/Lts/DDS/Core/topic_lock_master.h
@@ -7,10 +7,14 @@
 #include <Core/core_export.h>
 
 #if BUILD_RTI
-#include <Core/core_dtc.h>
+// Resolves to the codegen-generated core_dtc.h via the build-dir include
+// root (build4/Lts). The old <Core/core_dtc.h> spelling hit the migration
+// stub tree (include/Core/core_dtc.h), whose DDS::Core::Interface forward
+// declarations don't match the generated Core::Interface::Dtc.
+#include <DDS/Core/core_dtc.h>
 #else
 // Forward declarations for moc compatibility when BUILD_RTI=OFF
-namespace DDS { namespace Core { namespace Interface { class Dtc; } } }
+namespace Core { namespace Interface { class Dtc; } }
 #endif
 
 namespace DDSConnector
@@ -66,14 +70,16 @@ public:
   template<typename E>
   bool isLocked(const E &data, int exerciseId)
   {
-    auto it = m_lockedEntitys.constFind(key(data.id(), exerciseId, QString::fromStdString(typeid(E).name())));
+    // rtiddsgen -stl generates plain public data members, so the id is
+    // accessed directly instead of the old getter call data.id().
+    auto it = m_lockedEntitys.constFind(key(data.id, exerciseId, QString::fromStdString(typeid(E).name())));
     return !(it == m_lockedEntitys.cend());
   }
 
 private:
   QSet<key> m_lockedEntitys;
 #if BUILD_RTI
-  std::shared_ptr<DDS::Core::Interface::Dtc> m_coreDtc;
+  std::shared_ptr<Core::Interface::Dtc> m_coreDtc;
 #endif
 };