diff --git a/src/Nodeset.c b/src/Nodeset.c
index ac86e3c..a3b3c88 100644
--- a/src/Nodeset.c
+++ b/src/Nodeset.c
@@ -496,11 +496,22 @@ void Nodeset_newNodeFinish(Nodeset *nodeset, NL_Node *node)
 {
     if (!node->unknownRefs)
     {
-        Sort_addNode(nodeset->sortCtx, node);
-        if (node->nodeClass == NODECLASS_REFERENCETYPE)
+        if(!Sort_addNode(nodeset->sortCtx, node))
+        {
+            if (nodeset->logger)
+            {
+                nodeset->logger->log(nodeset->logger->context, NODESETLOADER_LOGLEVEL_ERROR,
+                            "node was not added to sorting algorithm, already exists");
+            }
+            Node_delete(node);
+        }
+        else
         {
-            nodeset->refService->addNewReferenceType(
-                nodeset->refService->context, (NL_ReferenceTypeNode *)node);
+            if (node->nodeClass == NODECLASS_REFERENCETYPE)
+            {
+                nodeset->refService->addNewReferenceType(
+                    nodeset->refService->context, (NL_ReferenceTypeNode *)node);
+            }
         }
     }
     else
diff --git a/src/Sort.c b/src/Sort.c
index f5abc12..9ee81c3 100644
--- a/src/Sort.c
+++ b/src/Sort.c
@@ -279,10 +279,15 @@ void Sort_cleanup(SortContext *ctx)
     free(ctx);
 }
 
-void Sort_addNode(SortContext *ctx, NL_Node *data) {
+bool Sort_addNode(SortContext *ctx, NL_Node *data) {
     S_Node *j = NULL;
     // add node, no matter if there are references on it
     j = search_node(ctx->root1, &data->id);
+    // entry already exists
+    if(j->data!=NULL)
+    {
+        return false;
+    }
     j->data = data;
     NL_Reference *hierachicalRef = data->hierachicalRefs;
     bool hierachicalRefRecorded = false;
@@ -303,7 +308,7 @@ void Sort_addNode(SortContext *ctx, NL_Node *data) {
         NL_InstanceNode *instanceNode = (NL_InstanceNode *)data;
         if(UA_NodeId_equal(&instanceNode->parentNodeId, &UA_NODEID_NULL))
         {
-            return;
+            return true;
         }
 
         S_Node *k = search_node(ctx->root1, &instanceNode->parentNodeId);
@@ -339,6 +344,7 @@ void Sort_addNode(SortContext *ctx, NL_Node *data) {
             data->hierachicalRefs = newRef;
         }
     }
+    return true;
 }
 
 bool Sort_start(SortContext *ctx, struct Nodeset *nodeset,
diff --git a/src/Sort.h b/src/Sort.h
index 10e38f2..047172f 100644
--- a/src/Sort.h
+++ b/src/Sort.h
@@ -22,7 +22,7 @@ struct NodesetLoader_Logger;
 typedef struct SortContext SortContext;
 SortContext* Sort_init(void);
 void Sort_cleanup(SortContext * ctx);
-void Sort_addNode(SortContext* ctx, struct NL_Node *node);
+bool Sort_addNode(SortContext* ctx, struct NL_Node *node);
 typedef void (*Sort_SortedNodeCallback)(struct Nodeset *nodeset, struct NL_Node *node);
 bool Sort_start(SortContext* ctx, struct Nodeset *nodeset, Sort_SortedNodeCallback callback, struct NodesetLoader_Logger* logger);