diff --git a/src/App/Document.cpp b/src/App/Document.cpp
index fc80d7069..b042326cf 100644
--- a/src/App/Document.cpp
+++ b/src/App/Document.cpp
@@ -1894,14 +1894,15 @@ DocumentObject * Document::addObject(const char* sType, const char* pObjectName,
     string ObjectName;
     if (!base)
         return 0;
-    if (!base->getTypeId().isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+    
+    App::DocumentObject* pcObject = dynamic_cast<App::DocumentObject*>(base);
+    if (!pcObject) {
         delete base;
         std::stringstream str;
         str << "'" << sType << "' is not a document object type";
         throw Base::TypeError(str.str());
     }
 
-    App::DocumentObject* pcObject = dynamic_cast<App::DocumentObject*>(base);
     pcObject->setDocument(this);
 
     // do no transactions if we do a rollback!
diff --git a/src/App/DocumentObject.h b/src/App/DocumentObject.h
index f6741985e..c1026b81a 100644
--- a/src/App/DocumentObject.h
+++ b/src/App/DocumentObject.h
@@ -259,5 +259,26 @@ protected: // attributes
 
 } //namespace App
 
+/**
+ * Overload of freecads base class cast for all cases without any virtual inheritance
+ */
+template<typename T> T * freecad_dynamic_cast(App::DocumentObject * t)
+{
+    if (t && t->isDerivedFrom(T::getClassTypeId()))
+        return static_cast<T*>(t);
+    else
+        return nullptr;
+}
+
+/**
+ * See explaination above
+ */
+template<typename T> const T * freecad_dynamic_cast(const App::DocumentObject * t)
+{
+    if (t && t->isDerivedFrom(T::getClassTypeId()))
+        return static_cast<const T*>(t);
+    else
+        return nullptr;
+}
 
 #endif // APP_DOCUMENTOBJECT_H
diff --git a/src/App/ExtensionContainerPyImp.cpp b/src/App/ExtensionContainerPyImp.cpp
index 1c47bd35a..284a8a736 100644
--- a/src/App/ExtensionContainerPyImp.cpp
+++ b/src/App/ExtensionContainerPyImp.cpp
@@ -149,7 +149,7 @@ PyObject* ExtensionContainerPy::addExtension(PyObject *args) {
         throw Py::Exception(Base::BaseExceptionFreeCADError,str.str());
     }    
     
-    ext->initExtension(dynamic_cast<App::DocumentObject*>(getExtensionContainerPtr()));
+    ext->initExtension(getExtensionContainerPtr());
     
     //set the proxy to allow python overrides
     App::Property* pp = ext->getPropertyByName("Proxy");
diff --git a/src/App/OriginGroupExtension.cpp b/src/App/OriginGroupExtension.cpp
index d98efdf18..afe14a519 100644
--- a/src/App/OriginGroupExtension.cpp
+++ b/src/App/OriginGroupExtension.cpp
@@ -70,13 +70,15 @@ App::DocumentObject *OriginGroupExtension::getGroupOfObject (const DocumentObjec
     std::vector<DocumentObject*> grps = doc->getObjectsWithExtension ( OriginGroupExtension::getClassTypeId() );
     for (auto grpObj: grps) {
         OriginGroupExtension* grp = dynamic_cast <OriginGroupExtension* >(grpObj->getExtension(OriginGroupExtension::getClassTypeId()));
+        if(!grp) throw Base::TypeError("Wrong type in origin group extenion");
+            
         if ( indirect ) {
             if ( grp->geoHasObject (obj) ) {
-                return dynamic_cast<App::DocumentObject*>(grp);
+                return grp->getExtendedObject();
             }
         } else {
             if ( grp->hasObject (obj) ) {
-                return dynamic_cast<App::DocumentObject*>(grp);
+                return grp->getExtendedObject();
             }
         }
     }
diff --git a/src/App/PropertyLinks.cpp b/src/App/PropertyLinks.cpp
index b44be4671..9e5466981 100644
--- a/src/App/PropertyLinks.cpp
+++ b/src/App/PropertyLinks.cpp
@@ -131,6 +131,7 @@ void PropertyLink::Restore(Base::XMLReader &reader)
 
     if (name != "") {
         DocumentObject* parent = dynamic_cast<DocumentObject*>(getContainer());
+        if(!parent) throw Base::TypeError("Property container is not document object");
         App::Document* document = parent->getDocument();
         DocumentObject* object = document ? document->getObject(name.c_str()) : 0;
         if (!object) {
@@ -289,6 +290,7 @@ void PropertyLinkList::Restore(Base::XMLReader &reader)
         // document. Thus, we should silently ingore this.
         // Property not in an object!
         DocumentObject* father = dynamic_cast<DocumentObject*>(getContainer());
+        if(!father) throw Base::TypeError("Property container is not document object");
         App::Document* document = father->getDocument();
         DocumentObject* child = document ? document->getObject(name.c_str()) : 0;
         if (child)
@@ -479,7 +481,10 @@ void PropertyLinkSub::Restore(Base::XMLReader &reader)
 
     DocumentObject *pcObject;
     if (!name.empty()) {
-        App::Document* document = dynamic_cast<DocumentObject*>(getContainer())->getDocument();
+        
+        auto* parent = dynamic_cast<DocumentObject*>(getContainer());
+        if(!parent) throw Base::TypeError("Property container is not document object");
+        App::Document* document = parent->getDocument();
         pcObject = document ? document->getObject(name.c_str()) : 0;
         if (!pcObject) {
             if (reader.isVerbose()) {
@@ -807,7 +812,6 @@ void PropertyLinkSubList::Restore(Base::XMLReader &reader)
     reader.readElement("LinkSubList");
     // get the value of my attribute
     int count = reader.getAttributeAsInteger("count");
-    assert(getContainer()->getTypeId().isDerivedFrom(App::DocumentObject::getClassTypeId()) );
 
     std::vector<DocumentObject*> values;
     values.reserve(count);
@@ -821,6 +825,7 @@ void PropertyLinkSubList::Restore(Base::XMLReader &reader)
         // document. Thus, we should silently ignore this.
         // Property not in an object!
         DocumentObject* father = dynamic_cast<DocumentObject*>(getContainer());
+        if(!father) throw Base::TypeError("Property container is not document object");
         App::Document* document = father->getDocument();
         DocumentObject* child = document ? document->getObject(name.c_str()) : 0;
         if (child)
diff --git a/src/Base/BaseClass.h b/src/Base/BaseClass.h
index 2e7622910..bfe49baa6 100644
--- a/src/Base/BaseClass.h
+++ b/src/Base/BaseClass.h
@@ -105,30 +105,24 @@ public:
 
 /**
  * Template that works just like dynamic_cast, but expects the argument to
- * inherit from Base::BaseClass.
+ * inherit from Base::BaseClass. Note thst for base class this is exactly the same as a dynamic_cast.
+ * The reason for that is that it is not possible to static_cast base to anything in the inheritance 
+ * chain after PropertyContainer. The reason for this is the used virtual inheritance.
+ * However, the function can be overload for different cast between objects in the inheritnce
+ * chain after PropertyContainer, for example from DocumentObject to all its derived types-
  *
  */
-
 template<typename T> T * freecad_dynamic_cast(Base::BaseClass * t)
 {
-    if (t && t->isDerivedFrom(T::getClassTypeId()))
-        return dynamic_cast<T*>(t);
-    else
-        return 0;
+    return dynamic_cast<T*>(t);
 }
 
 /**
- * Template that works just like dynamic_cast, but expects the argument to
- * inherit from a const Base::BaseClass.
- *
+ * See explaination above
  */
-
 template<typename T> const T * freecad_dynamic_cast(const Base::BaseClass * t)
 {
-    if (t && t->isDerivedFrom(T::getClassTypeId()))
-        return dynamic_cast<const T*>(t);
-    else
-        return 0;
+    return dynamic_cast<const T*>(t);
 }
 
 
diff --git a/src/Gui/ViewProviderGeoFeatureGroupExtension.cpp b/src/Gui/ViewProviderGeoFeatureGroupExtension.cpp
index ba532f0cb..867e2d87f 100644
--- a/src/Gui/ViewProviderGeoFeatureGroupExtension.cpp
+++ b/src/Gui/ViewProviderGeoFeatureGroupExtension.cpp
@@ -53,7 +53,7 @@ ViewProviderGeoFeatureGroupExtension::~ViewProviderGeoFeatureGroupExtension()
 
 std::vector<App::DocumentObject*> ViewProviderGeoFeatureGroupExtension::extensionClaimChildren3D(void) const {
     auto* ext = getExtendedViewProvider()->getObject()->getExtensionByType<App::GeoFeatureGroupExtension>();
-    return ext->getGeoSubObjects();
+    return ext ? ext->getGeoSubObjects() : std::vector<App::DocumentObject*>();
 }
 
 void ViewProviderGeoFeatureGroupExtension::extensionAttach(App::DocumentObject* pcObject)
@@ -84,7 +84,7 @@ std::vector<std::string> ViewProviderGeoFeatureGroupExtension::extensionGetDispl
 void ViewProviderGeoFeatureGroupExtension::extensionUpdateData(const App::Property* prop)
 {
     auto obj = getExtendedViewProvider()->getObject()->getExtensionByType<App::GeoFeatureGroupExtension>();
-    if (prop == &obj->Placement) {
+    if (obj && prop == &obj->Placement) {
         getExtendedViewProvider()->setTransformation ( obj->Placement.getValue().toMatrix() );
     } else {
         ViewProviderGroupExtension::extensionUpdateData ( prop );
diff --git a/src/Gui/ViewProviderOriginGroupExtension.cpp b/src/Gui/ViewProviderOriginGroupExtension.cpp
index e22121b23..45e8a7139 100644
--- a/src/Gui/ViewProviderOriginGroupExtension.cpp
+++ b/src/Gui/ViewProviderOriginGroupExtension.cpp
@@ -61,6 +61,9 @@ std::vector<App::DocumentObject*> ViewProviderOriginGroupExtension::constructChi
         const std::vector<App::DocumentObject*> &children ) const
 {
     auto* group = getExtendedViewProvider()->getObject()->getExtensionByType<App::OriginGroupExtension>();
+    if(!group)
+        return children;
+    
     App::DocumentObject *originObj = group->Origin.getValue();
 
     // Origin must be first
@@ -102,7 +105,7 @@ void ViewProviderOriginGroupExtension::extensionAttach(App::DocumentObject *pcOb
 void ViewProviderOriginGroupExtension::extensionUpdateData( const App::Property* prop ) {
     
     auto* group = getExtendedViewProvider()->getObject()->getExtensionByType<App::OriginGroupExtension>();
-    if ( prop == &group->Group ) {
+    if ( group && prop == &group->Group ) {
         updateOriginSize();
     }
 
@@ -111,7 +114,7 @@ void ViewProviderOriginGroupExtension::extensionUpdateData( const App::Property*
 
 void ViewProviderOriginGroupExtension::slotChangedObjectApp ( const App::DocumentObject& obj) {
     auto* group = getExtendedViewProvider()->getObject()->getExtensionByType<App::OriginGroupExtension>();
-    if ( group->hasObject (&obj, /*recusive=*/ true ) ) {
+    if ( group && group->hasObject (&obj, /*recusive=*/ true ) ) {
         updateOriginSize ();
     }
 }
@@ -132,6 +135,8 @@ void ViewProviderOriginGroupExtension::slotChangedObjectGui ( const Gui::ViewPro
 
 void ViewProviderOriginGroupExtension::updateOriginSize () {
     auto* group = getExtendedViewProvider()->getObject()->getExtensionByType<App::OriginGroupExtension>();
+    if(!group)
+        return;
 
     // obtain an Origin and it's ViewProvider
     App::Origin* origin = 0;
diff --git a/src/Gui/propertyeditor/PropertyItem.cpp b/src/Gui/propertyeditor/PropertyItem.cpp
index 0180b61ec..23533541b 100644
--- a/src/Gui/propertyeditor/PropertyItem.cpp
+++ b/src/Gui/propertyeditor/PropertyItem.cpp
@@ -288,8 +288,8 @@ QString PropertyItem::pythonIdentifier(const App::Property* prop) const
         QString propName = QString::fromLatin1(parent->getPropertyName(prop));
         return QString::fromLatin1("FreeCAD.getDocument(\"%1\").%2").arg(docName).arg(propName);
     }
-    if (parent->getTypeId().isDerivedFrom(App::DocumentObject::getClassTypeId())) {
-        App::DocumentObject* obj = dynamic_cast<App::DocumentObject*>(parent);
+    App::DocumentObject* obj = dynamic_cast<App::DocumentObject*>(parent);
+    if (obj) {
         App::Document* doc = obj->getDocument();
         QString docName = QString::fromLatin1(App::GetApplication().getDocumentName(doc));
         QString objName = QString::fromLatin1(obj->getNameInDocument());
@@ -3375,13 +3375,12 @@ QVariant PropertyLinkItem::value(const App::Property* prop) const
     else {
         // no object assigned
         // the document name
-        if (c->getTypeId().isDerivedFrom(App::DocumentObject::getClassTypeId())) {
-            App::DocumentObject* obj = dynamic_cast<App::DocumentObject*>(c);
+        App::DocumentObject* obj = dynamic_cast<App::DocumentObject*>(c);
+        if (obj)            
             list << QString::fromLatin1(obj->getDocument()->getName());
-        }
-        else {
+        else
             list << QString::fromLatin1("");
-        }
+  
         // the internal object name
         list << QString::fromLatin1("Null");
         // the object label
@@ -3389,13 +3388,11 @@ QVariant PropertyLinkItem::value(const App::Property* prop) const
     }
 
     // the name of this object
-    if (c->getTypeId().isDerivedFrom(App::DocumentObject::getClassTypeId())) {
-        App::DocumentObject* obj = dynamic_cast<App::DocumentObject*>(c);
-        list << QString::fromLatin1(obj->getNameInDocument());
-    }
-    else {
+    App::DocumentObject* cobj = dynamic_cast<App::DocumentObject*>(c);
+    if (cobj)
+        list << QString::fromLatin1(cobj->getNameInDocument());
+    else 
         list << QString::fromLatin1("Null");
-    }
 
     return QVariant(list);
 }
diff --git a/src/Mod/Fem/App/PropertyPostDataObject.cpp b/src/Mod/Fem/App/PropertyPostDataObject.cpp
index 7e27d6aaf..3d8ce7cc5 100644
--- a/src/Mod/Fem/App/PropertyPostDataObject.cpp
+++ b/src/Mod/Fem/App/PropertyPostDataObject.cpp
@@ -263,10 +263,11 @@ void PropertyPostDataObject::SaveDocFile (Base::Writer &writer) const
         // We only print an error message but continue writing the next files to the
         // stream...
         App::PropertyContainer* father = this->getContainer();
-        if (father && father->isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+        if (father) {
             App::DocumentObject* obj = dynamic_cast<App::DocumentObject*>(father);
-            Base::Console().Error("Dataset of '%s' cannot be written to vtk file '%s'\n",
-                obj->Label.getValue(),fi.filePath().c_str());
+            if(obj) 
+                Base::Console().Error("Dataset of '%s' cannot be written to vtk file '%s'\n",
+                    obj->Label.getValue(),fi.filePath().c_str());
         }
         else {
             Base::Console().Error("Cannot save vtk file '%s'\n", fi.filePath().c_str());
@@ -331,10 +332,11 @@ void PropertyPostDataObject::RestoreDocFile(Base::Reader &reader)
             // We only print an error message but continue reading the next files from the
             // stream...
             App::PropertyContainer* father = this->getContainer();
-            if (father && father->isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+            if (father) {
                 App::DocumentObject* obj = dynamic_cast<App::DocumentObject*>(father);
-                Base::Console().Error("Dataset file '%s' with data of '%s' seems to be empty\n",
-                    fi.filePath().c_str(),obj->Label.getValue());
+                if(obj)
+                    Base::Console().Error("Dataset file '%s' with data of '%s' seems to be empty\n",
+                        fi.filePath().c_str(),obj->Label.getValue());
             }
             else {
                 Base::Console().Warning("Loaded Dataset file '%s' seems to be empty\n", fi.filePath().c_str());
diff --git a/src/Mod/Part/App/PropertyTopoShape.cpp b/src/Mod/Part/App/PropertyTopoShape.cpp
index 3b4b775b8..a24bbb23f 100644
--- a/src/Mod/Part/App/PropertyTopoShape.cpp
+++ b/src/Mod/Part/App/PropertyTopoShape.cpp
@@ -296,10 +296,11 @@ void PropertyPartShape::SaveDocFile (Base::Writer &writer) const
                 // We only print an error message but continue writing the next files to the
                 // stream...
                 App::PropertyContainer* father = this->getContainer();
-                if (father && father->isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+                if (father) {
                     App::DocumentObject* obj = dynamic_cast<App::DocumentObject*>(father);
-                    Base::Console().Error("Shape of '%s' cannot be written to BRep file '%s'\n", 
-                        obj->Label.getValue(),fi.filePath().c_str());
+                    if(obj)
+                        Base::Console().Error("Shape of '%s' cannot be written to BRep file '%s'\n", 
+                            obj->Label.getValue(),fi.filePath().c_str());
                 }
                 else {
                     Base::Console().Error("Cannot save BRep file '%s'\n", fi.filePath().c_str());
@@ -375,10 +376,11 @@ void PropertyPartShape::RestoreDocFile(Base::Reader &reader)
                     // We only print an error message but continue reading the next files from the
                     // stream...
                     App::PropertyContainer* father = this->getContainer();
-                    if (father && father->isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+                    if (father) {
                         App::DocumentObject* obj = dynamic_cast<App::DocumentObject*>(father);
-                        Base::Console().Error("BRep file '%s' with shape of '%s' seems to be empty\n", 
-                            fi.filePath().c_str(),obj->Label.getValue());
+                        if(obj)
+                            Base::Console().Error("BRep file '%s' with shape of '%s' seems to be empty\n", 
+                                fi.filePath().c_str(),obj->Label.getValue());
                     }
                     else {
                         Base::Console().Warning("Loaded BRep file '%s' seems to be empty\n", fi.filePath().c_str());
diff --git a/src/Mod/PartDesign/Gui/Command.cpp b/src/Mod/PartDesign/Gui/Command.cpp
index 5df71fc61..7c573e4f7 100644
--- a/src/Mod/PartDesign/Gui/Command.cpp
+++ b/src/Mod/PartDesign/Gui/Command.cpp
@@ -442,7 +442,7 @@ void CmdPartDesignNewSketch::activated(int iMsg)
         auto group = App::GeoFeatureGroupExtension::getGroupOfObject ( pcActiveBody );
         App::GeoFeatureGroupExtension* geoGroup = nullptr;
         if(group)
-            geoGroup = dynamic_cast<App::GeoFeatureGroupExtension*>(group->getExtension(App::GeoFeatureGroupExtension::getClassTypeId()));
+            geoGroup = group->getExtensionByType<App::GeoFeatureGroupExtension>();
 
         std::vector<App::DocumentObject*> planes;
         std::vector<PartDesignGui::TaskFeaturePick::featureStatus> status;
diff --git a/src/Mod/PartDesign/Gui/ViewProviderDatum.cpp b/src/Mod/PartDesign/Gui/ViewProviderDatum.cpp
index b44758166..5e1a6c4cf 100644
--- a/src/Mod/PartDesign/Gui/ViewProviderDatum.cpp
+++ b/src/Mod/PartDesign/Gui/ViewProviderDatum.cpp
@@ -330,7 +330,9 @@ SbBox3f ViewProviderDatum::getRelevantBoundBox () const {
         App::DocumentObject* group =  App::DocumentObjectGroup::getGroupOfObject ( this->getObject () );
 
         if(group) {
-            objs = dynamic_cast<App::GroupExtension*>(group->getExtension(App::GroupExtension::getClassTypeId()))->getObjects ();
+            auto* ext = group->getExtensionByType<App::GroupExtension>();
+            if(ext) 
+                objs = ext->getObjects ();
         } else {
             // Fallback to whole document
             objs = this->getObject ()->getDocument ()->getObjects ();