diff --git a/src/App/CMakeLists.txt b/src/App/CMakeLists.txt
index 9ad7024b87..00b7b41b1c 100644
--- a/src/App/CMakeLists.txt
+++ b/src/App/CMakeLists.txt
@@ -15,7 +15,7 @@ ENDIF(DOCDIR)
 add_definitions(-DBOOST_${Boost_VERSION})
 
 #if you want to use the old DAG structure uncomment this line
-add_definitions(-DUSE_OLD_DAG)
+#add_definitions(-DUSE_OLD_DAG)
 
 #write relevant cmake variables to a file for later access with python. Exportet are all variables 
 #starting with BUILD. As the variable only exists if the user set it to ON a dict is useless, we 
diff --git a/src/App/Document.cpp b/src/App/Document.cpp
index 367f4f46a9..1ca81eb978 100644
--- a/src/App/Document.cpp
+++ b/src/App/Document.cpp
@@ -2199,8 +2199,8 @@ std::vector<App::DocumentObject*> Document::topologicalSort() const
     ret.reserve(d->objectArray.size());
     map < App::DocumentObject*,int > countMap;
 
-    for (auto objectIt : d->objectArray)
-        countMap[objectIt] = objectIt->getInList().size();
+    for (auto objectIt : d->objectMap)
+        countMap[objectIt.second] = objectIt.second->getInList().size();
 
     auto rootObjeIt = find_if(countMap.begin(), countMap.end(), [](pair < App::DocumentObject*, int > count)->bool {
         return count.second == 0;
@@ -2213,7 +2213,13 @@ std::vector<App::DocumentObject*> Document::topologicalSort() const
 
     while (rootObjeIt != countMap.end()){
         rootObjeIt->second = rootObjeIt->second - 1;
-        for (auto outListIt : rootObjeIt->first->getOutList()){
+        
+        //we need outlist with unique entries, as inlist also has unique entries
+        auto out = rootObjeIt->first->getOutList();
+        std::sort(out.begin(), out.end());
+        out.erase(std::unique(out.begin(), out.end()), out.end());
+        
+        for (auto outListIt : out) {
             auto outListMapIt = countMap.find(outListIt);
             outListMapIt->second = outListMapIt->second - 1;
         }
diff --git a/src/App/DocumentPy.xml b/src/App/DocumentPy.xml
index 3752239688..4d4dfb0d0a 100644
--- a/src/App/DocumentPy.xml
+++ b/src/App/DocumentPy.xml
@@ -151,7 +151,7 @@ Both parameters are optional.</UserDocu>
       </Documentation>
       <Parameter Name="Objects" Type="List" />
     </Attribute>
-    <Attribute Name="ToplogicalSortedObjects" ReadOnly="true">
+    <Attribute Name="TopologicalSortedObjects" ReadOnly="true">
       <Documentation>
         <UserDocu>The list of object of this document in topological sorted order</UserDocu>
       </Documentation>
diff --git a/src/App/DocumentPyImp.cpp b/src/App/DocumentPyImp.cpp
index e3d2303df4..506c31cfc0 100644
--- a/src/App/DocumentPyImp.cpp
+++ b/src/App/DocumentPyImp.cpp
@@ -516,7 +516,7 @@ Py::List DocumentPy::getObjects(void) const
     return res;
 }
 
-Py::List DocumentPy::getToplogicalSortedObjects(void) const
+Py::List DocumentPy::getTopologicalSortedObjects(void) const
 {
     std::vector<DocumentObject*> objs = getDocumentPtr()->topologicalSort();
     Py::List res;
diff --git a/src/App/PropertyLinks.cpp b/src/App/PropertyLinks.cpp
index 679315f013..728ad59344 100644
--- a/src/App/PropertyLinks.cpp
+++ b/src/App/PropertyLinks.cpp
@@ -75,11 +75,13 @@ void PropertyLink::setValue(App::DocumentObject * lValue)
 {
     aboutToSetValue();
 #ifndef USE_OLD_DAG
-    // maintain the back link in the DocumentObject class
-    if(_pcLink)
-        _pcLink->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
-    if(lValue)
-        lValue->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    // maintain the back link in the DocumentObject class if it is from a document object
+    if(getContainer() && getContainer()->isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+        if(_pcLink)
+            _pcLink->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
+        if(lValue)
+            lValue->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    }
 #endif
     _pcLink=lValue;
     hasSetValue();
@@ -208,10 +210,12 @@ void PropertyLinkList::setValue(DocumentObject* lValue)
 {
 #ifndef USE_OLD_DAG   
     //maintain the back link in the DocumentObject class
-    for(auto *obj : _lValueList)
-        obj->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
-    if(lValue)
-        lValue->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    if(getContainer() && getContainer()->isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+        for(auto *obj : _lValueList)
+            obj->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
+        if(lValue)
+            lValue->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    }
 #endif
     
     if (lValue){
@@ -232,10 +236,12 @@ void PropertyLinkList::setValues(const std::vector<DocumentObject*>& lValue)
     aboutToSetValue();
 #ifndef USE_OLD_DAG
     //maintain the back link in the DocumentObject class
-    for(auto *obj : _lValueList)
-        obj->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
-    for(auto *obj : lValue)
-        obj->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    if(getContainer() && getContainer()->isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+        for(auto *obj : _lValueList)
+            obj->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
+        for(auto *obj : lValue)
+            obj->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    }
 #endif
     _lValueList = lValue;
     hasSetValue();
@@ -391,10 +397,12 @@ void PropertyLinkSub::setValue(App::DocumentObject * lValue, const std::vector<s
 {
     aboutToSetValue();
 #ifndef USE_OLD_DAG
-    if (_pcLinkSub)
-        _pcLinkSub->_removeBackLink(static_cast<App::DocumentObject*>(getContainer()));
-    if (lValue)
-        lValue->_addBackLink(static_cast<App::DocumentObject*>(getContainer()));
+    if(getContainer() && getContainer()->isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+        if (_pcLinkSub)
+            _pcLinkSub->_removeBackLink(static_cast<App::DocumentObject*>(getContainer()));
+        if (lValue)
+            lValue->_addBackLink(static_cast<App::DocumentObject*>(getContainer()));
+    }
 #endif
     _pcLinkSub=lValue;
     _cSubList = SubList;
@@ -587,10 +595,12 @@ void PropertyLinkSubList::setValue(DocumentObject* lValue,const char* SubName)
 {
 #ifndef USE_OLD_DAG
     //maintain backlinks
-    for(auto *obj : _lValueList)
-        obj->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
-    if (lValue)
-        lValue->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    if(getContainer() && getContainer()->isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+        for(auto *obj : _lValueList)
+            obj->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
+        if (lValue)
+            lValue->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    }
 #endif
     
     if (lValue) {
@@ -615,15 +625,19 @@ void PropertyLinkSubList::setValues(const std::vector<DocumentObject*>& lValue,c
         throw Base::ValueError("PropertyLinkSubList::setValues: size of subelements list != size of objects list");
     
 #ifndef USE_OLD_DAG
-    //maintain backlinks. _lValueList can contain items multiple times, but we trust the document 
-    //object to ensure that this works
-    for(auto *obj : _lValueList)
-        obj->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
-    
-    //maintain backlinks. lValue can contain items multiple times, but we trust the document 
-    //object to ensure that the backlink is only added once
-    for(auto *obj : lValue)
-        obj->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    //maintain backlinks. 
+    if(getContainer() && getContainer()->isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+        
+        //_lValueList can contain items multiple times, but we trust the document 
+        //object to ensure that this works
+        for(auto *obj : _lValueList)
+            obj->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
+        
+        //maintain backlinks. lValue can contain items multiple times, but we trust the document 
+        //object to ensure that the backlink is only added once
+        for(auto *obj : lValue)
+            obj->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    }
 #endif
     
     aboutToSetValue();
@@ -641,15 +655,19 @@ void PropertyLinkSubList::setValues(const std::vector<DocumentObject*>& lValue,c
         throw Base::ValueError("PropertyLinkSubList::setValues: size of subelements list != size of objects list");
     
 #ifndef USE_OLD_DAG
-    //maintain backlinks. _lValueList can contain items multiple times, but we trust the document 
-    //object to ensure that this works
-    for(auto *obj : _lValueList)
-        obj->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
-    
-    //maintain backlinks. lValue can contain items multiple times, but we trust the document 
-    //object to ensure that the backlink is only added once
-    for(auto *obj : lValue)
-        obj->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    //maintain backlinks. 
+    if(getContainer() && getContainer()->isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+        
+        //_lValueList can contain items multiple times, but we trust the document 
+        //object to ensure that this works
+        for(auto *obj : _lValueList)
+            obj->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
+        
+        //maintain backlinks. lValue can contain items multiple times, but we trust the document 
+        //object to ensure that the backlink is only added once
+        for(auto *obj : lValue)
+            obj->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    }
 #endif
     
     aboutToSetValue();
@@ -660,16 +678,20 @@ void PropertyLinkSubList::setValues(const std::vector<DocumentObject*>& lValue,c
 
 void PropertyLinkSubList::setValue(DocumentObject* lValue, const std::vector<string> &SubList)
 {
-#ifndef USE_OLD_DAG    
-    //maintain backlinks. _lValueList can contain items multiple times, but we trust the document 
-    //object to ensure that this works
-    for(auto *obj : _lValueList)
-        obj->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
-    
-    //maintain backlinks. lValue can contain items multiple times, but we trust the document 
-    //object to ensure that the backlink is only added once
-    if(lValue)
-        lValue->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+#ifndef USE_OLD_DAG   
+    //maintain backlinks.
+    if(getContainer() && getContainer()->isDerivedFrom(App::DocumentObject::getClassTypeId())) {
+        
+        //_lValueList can contain items multiple times, but we trust the document 
+        //object to ensure that this works
+        for(auto *obj : _lValueList)
+            obj->_removeBackLink(static_cast<DocumentObject*>(getContainer()));
+        
+        //maintain backlinks. lValue can contain items multiple times, but we trust the document 
+        //object to ensure that the backlink is only added once
+        if(lValue)
+            lValue->_addBackLink(static_cast<DocumentObject*>(getContainer()));
+    }
 #endif
     
     aboutToSetValue();