diff --git a/Source/API/lib3mf_meshobject.cpp b/Source/API/lib3mf_meshobject.cpp
index bb2976c0..d8d71d97 100644
--- a/Source/API/lib3mf_meshobject.cpp
+++ b/Source/API/lib3mf_meshobject.cpp
@@ -428,8 +428,8 @@ void CMeshObject::SetVolumeData(IVolumeData* pTheVolumeData)
 }
 
 ITriangleSet* CMeshObject::AddTriangleSet(const std::string& sIdentifier, const std::string& sName)
-{
-	return new CTriangleSet(NMR::CModelTriangleSet::make (sIdentifier, sName), meshObject());
+{	
+	return new CTriangleSet(meshObject()->addTriangleSet(sIdentifier, sName), meshObject());
 }
 
 bool CMeshObject::HasTriangleSet(const std::string& sIdentifier)
diff --git a/Source/Model/Writer/v100/NMR_ModelWriterNode100_Model.cpp b/Source/Model/Writer/v100/NMR_ModelWriterNode100_Model.cpp
index 8b719cbc..fc586f66 100644
--- a/Source/Model/Writer/v100/NMR_ModelWriterNode100_Model.cpp
+++ b/Source/Model/Writer/v100/NMR_ModelWriterNode100_Model.cpp
@@ -168,7 +168,7 @@ namespace NMR {
 		}
 
 		if (m_bWriteTriangleSetExtension) {
-			writeConstPrefixedStringAttribute(XML_3MF_ATTRIBUTE_XMLNS, XML_3MF_NAMESPACEPREFIX_SLICE, XML_3MF_NAMESPACE_TRIANGLESETS);
+			writeConstPrefixedStringAttribute(XML_3MF_ATTRIBUTE_XMLNS, XML_3MF_NAMESPACEPREFIX_TRIANGLESETS, XML_3MF_NAMESPACE_TRIANGLESETS);
 			if (m_pModel->RequireExtension(XML_3MF_NAMESPACE_TRIANGLESETS)) {
 				if (sRequiredExtensions.size() > 0)
 					sRequiredExtensions = sRequiredExtensions + " ";