diff --git a/src/blackgui/guiapplication.cpp b/src/blackgui/guiapplication.cpp
index 7aa377eed..aee11bf0e 100644
--- a/src/blackgui/guiapplication.cpp
+++ b/src/blackgui/guiapplication.cpp
@@ -122,7 +122,7 @@ namespace BlackGui
 
     IMainWindowAccess *CGuiApplication::mainWindowAccess()
     {
-        IMainWindowAccess *m = dynamic_cast<IMainWindowAccess *>(mainApplicationWindow());
+        IMainWindowAccess *m = qobject_cast<IMainWindowAccess *>(mainApplicationWindow());
         return m;
     }
 
diff --git a/src/blackgui/guiapplication.h b/src/blackgui/guiapplication.h
index ea5fe650e..a4876085a 100644
--- a/src/blackgui/guiapplication.h
+++ b/src/blackgui/guiapplication.h
@@ -47,6 +47,7 @@ namespace BlackGui
         public BlackGui::IMainWindowAccess
     {
         Q_OBJECT
+        Q_INTERFACES(BlackGui::IMainWindowAccess)
 
     public:
         //! Similar to \sa QCoreApplication::instance() returns the single instance
diff --git a/src/blackgui/mainwindowaccess.h b/src/blackgui/mainwindowaccess.h
index e0df2ba62..8330b21e1 100644
--- a/src/blackgui/mainwindowaccess.h
+++ b/src/blackgui/mainwindowaccess.h
@@ -45,4 +45,6 @@ namespace BlackGui
     };
 } // ns
 
+Q_DECLARE_INTERFACE(BlackGui::IMainWindowAccess, "org.swift-project.blackgui.mainwindowaccess")
+
 #endif // guard
diff --git a/src/swiftcore/swiftcore.h b/src/swiftcore/swiftcore.h
index 70c8dd814..4eac221ec 100644
--- a/src/swiftcore/swiftcore.h
+++ b/src/swiftcore/swiftcore.h
@@ -31,6 +31,7 @@ class CSwiftCore :
     public BlackMisc::CIdentifiable
 {
     Q_OBJECT
+    Q_INTERFACES(BlackGui::IMainWindowAccess)
 
 public:
     //! Constructor
diff --git a/src/swiftdata/swiftdata.h b/src/swiftdata/swiftdata.h
index e5fddb453..506487106 100644
--- a/src/swiftdata/swiftdata.h
+++ b/src/swiftdata/swiftdata.h
@@ -35,6 +35,7 @@ class CSwiftData :
     public BlackGui::IMainWindowAccess
 {
     Q_OBJECT
+    Q_INTERFACES(BlackGui::IMainWindowAccess)
 
 public:
     //! Constructor
diff --git a/src/swiftguistandard/swiftguistd.h b/src/swiftguistandard/swiftguistd.h
index 812c824d8..625457a06 100644
--- a/src/swiftguistandard/swiftguistd.h
+++ b/src/swiftguistandard/swiftguistd.h
@@ -49,6 +49,7 @@ class SwiftGuiStd :
     public BlackGui::IMainWindowAccess
 {
     Q_OBJECT
+    Q_INTERFACES(BlackGui::IMainWindowAccess)
 
 public:
     //! Main page indexes
diff --git a/src/swiftlauncher/swiftlauncher.h b/src/swiftlauncher/swiftlauncher.h
index 71c547546..f52ea351b 100644
--- a/src/swiftlauncher/swiftlauncher.h
+++ b/src/swiftlauncher/swiftlauncher.h
@@ -37,6 +37,7 @@ class CSwiftLauncher :
     public BlackGui::IMainWindowAccess
 {
     Q_OBJECT
+    Q_INTERFACES(BlackGui::IMainWindowAccess)
 
 public:
     //! Constructor