diff --git a/include/QtNodes/internal/ConnectionIdUtils.hpp b/include/QtNodes/internal/ConnectionIdUtils.hpp
index 7f70a1b4b..a77272195 100644
--- a/include/QtNodes/internal/ConnectionIdUtils.hpp
+++ b/include/QtNodes/internal/ConnectionIdUtils.hpp
@@ -130,20 +130,21 @@ inline QJsonObject toJson(ConnectionId const &connId)
 {
     QJsonObject connJson;
 
-    connJson["outNodeId"] = static_cast<qint64>(connId.outNodeId);
-    connJson["outPortIndex"] = static_cast<qint64>(connId.outPortIndex);
-    connJson["intNodeId"] = static_cast<qint64>(connId.inNodeId);
-    connJson["inPortIndex"] = static_cast<qint64>(connId.inPortIndex);
+    connJson[QLatin1String("outNodeId")] = static_cast<qint64>(connId.outNodeId);
+    connJson[QLatin1String("outPortIndex")] = static_cast<qint64>(connId.outPortIndex);
+    connJson[QLatin1String("intNodeId")] = static_cast<qint64>(connId.inNodeId);
+    connJson[QLatin1String("inPortIndex")] = static_cast<qint64>(connId.inPortIndex);
 
     return connJson;
 }
 
 inline ConnectionId fromJson(QJsonObject const &connJson)
 {
-    ConnectionId connId{static_cast<NodeId>(connJson["outNodeId"].toInt(InvalidNodeId)),
-                        static_cast<PortIndex>(connJson["outPortIndex"].toInt(InvalidPortIndex)),
-                        static_cast<NodeId>(connJson["intNodeId"].toInt(InvalidNodeId)),
-                        static_cast<PortIndex>(connJson["inPortIndex"].toInt(InvalidPortIndex))};
+    ConnectionId connId{
+        static_cast<NodeId>(connJson[QLatin1String("outNodeId")].toInt(InvalidNodeId)),
+        static_cast<PortIndex>(connJson[QLatin1String("outPortIndex")].toInt(InvalidPortIndex)),
+        static_cast<NodeId>(connJson[QLatin1String("intNodeId")].toInt(InvalidNodeId)),
+        static_cast<PortIndex>(connJson[QLatin1String("inPortIndex")].toInt(InvalidPortIndex))};
 
     return connId;
 }
diff --git a/include/QtNodes/internal/DataFlowGraphModel.hpp b/include/QtNodes/internal/DataFlowGraphModel.hpp
index 268800202..cc8277a59 100644
--- a/include/QtNodes/internal/DataFlowGraphModel.hpp
+++ b/include/QtNodes/internal/DataFlowGraphModel.hpp
@@ -94,17 +94,23 @@ class NODE_EDITOR_PUBLIC DataFlowGraphModel : public AbstractGraphModel, public
         return model;
     }
 
+public Q_SLOTS:
+    virtual void propagate(NodeId const nodeId);
+
+protected:
+    virtual bool canPropagate(ConnectionId const) const { return true; };
+
 Q_SIGNALS:
     void inPortDataWasSet(NodeId const, PortType const, PortIndex const);
 
 private:
     NodeId newNodeId() override { return _nextNodeId++; }
 
+protected Q_SLOTS:
     void sendConnectionCreation(ConnectionId const connectionId);
 
     void sendConnectionDeletion(ConnectionId const connectionId);
 
-private Q_SLOTS:
     /**
    * Fuction is called in three cases:
    *
@@ -115,10 +121,10 @@ private Q_SLOTS:
    * - When a node restored from JSON an needs to send data downstream.
    *   @see DataFlowGraphModel::loadNode
    */
-    void onOutPortDataUpdated(NodeId const nodeId, PortIndex const portIndex);
+    virtual void onOutPortDataUpdated(NodeId const nodeId, PortIndex const portIndex);
 
     /// Function is called after detaching a connection.
-    void propagateEmptyDataTo(NodeId const nodeId, PortIndex const portIndex);
+    virtual void propagateEmptyDataTo(NodeId const nodeId, PortIndex const portIndex);
 
 private:
     std::shared_ptr<NodeDelegateModelRegistry> _registry;
diff --git a/include/QtNodes/internal/NodeDelegateModelRegistry.hpp b/include/QtNodes/internal/NodeDelegateModelRegistry.hpp
index 4f230a4f4..a2060160d 100644
--- a/include/QtNodes/internal/NodeDelegateModelRegistry.hpp
+++ b/include/QtNodes/internal/NodeDelegateModelRegistry.hpp
@@ -41,7 +41,7 @@ class NODE_EDITOR_PUBLIC NodeDelegateModelRegistry
 
 public:
     template<typename ModelType>
-    void registerModel(RegistryItemCreator creator, QString const &category = "Nodes")
+    void registerModel(RegistryItemCreator creator, QString const &category = QLatin1String("Nodes"))
     {
         QString const name = computeName<ModelType>(HasStaticMethodName<ModelType>{}, creator);
         if (!_registeredItemCreators.count(name)) {
@@ -52,7 +52,7 @@ class NODE_EDITOR_PUBLIC NodeDelegateModelRegistry
     }
 
     template<typename ModelType>
-    void registerModel(QString const &category = "Nodes")
+    void registerModel(QString const &category = QLatin1String("Nodes"))
     {
         RegistryItemCreator creator = []() { return std::make_unique<ModelType>(); };
         registerModel<ModelType>(std::move(creator), category);
@@ -62,7 +62,7 @@ class NODE_EDITOR_PUBLIC NodeDelegateModelRegistry
   template<typename ModelType>
   void
   registerModel(RegistryItemCreator creator,
-                QString const&      category = "Nodes")
+                QString const&      category = QLatin1String("Nodes"))
   {
     registerModel<ModelType>(std::move(creator), category);
   }
@@ -70,7 +70,7 @@ class NODE_EDITOR_PUBLIC NodeDelegateModelRegistry
 
   template <typename ModelCreator>
   void
-  registerModel(ModelCreator&& creator, QString const& category = "Nodes")
+  registerModel(ModelCreator&& creator, QString const& category = QLatin1String("Nodes"))
   {
     using ModelType = compute_model_type_t<decltype(creator())>;
     registerModel<ModelType>(std::forward<ModelCreator>(creator), category);
diff --git a/src/DataFlowGraphModel.cpp b/src/DataFlowGraphModel.cpp
index a5ba8734f..f75803218 100644
--- a/src/DataFlowGraphModel.cpp
+++ b/src/DataFlowGraphModel.cpp
@@ -138,12 +138,13 @@ void DataFlowGraphModel::addConnection(ConnectionId const connectionId)
                                                   PortType::Out,
                                                   connectionId.outPortIndex,
                                                   PortRole::Data);
-
-    setPortData(connectionId.inNodeId,
-                PortType::In,
-                connectionId.inPortIndex,
-                portDataToPropagate,
-                PortRole::Data);
+    if (canPropagate(connectionId)) {
+        setPortData(connectionId.inNodeId,
+                    PortType::In,
+                    connectionId.inPortIndex,
+                    portDataToPropagate,
+                    PortRole::Data);
+    }
 }
 
 void DataFlowGraphModel::sendConnectionCreation(ConnectionId const connectionId)
@@ -518,7 +519,21 @@ void DataFlowGraphModel::onOutPortDataUpdated(NodeId const nodeId, PortIndex con
     QVariant const portDataToPropagate = portData(nodeId, PortType::Out, portIndex, PortRole::Data);
 
     for (auto const &cn : connected) {
-        setPortData(cn.inNodeId, PortType::In, cn.inPortIndex, portDataToPropagate, PortRole::Data);
+        if (canPropagate(cn)) {
+            setPortData(cn.inNodeId,
+                        PortType::In,
+                        cn.inPortIndex,
+                        portDataToPropagate,
+                        PortRole::Data);
+        }
+    }
+}
+
+void DataFlowGraphModel::propagate(NodeId const nodeId)
+{
+    unsigned int nPorts = nodeData(nodeId, NodeRole::OutPortCount).toUInt();
+    for (PortIndex idx = 0; idx < nPorts; ++idx) {
+        onOutPortDataUpdated(nodeId, idx);
     }
 }