diff --git a/toonz/sources/toonzqt/fxselection.cpp b/toonz/sources/toonzqt/fxselection.cpp
index b93da1e..20e03ef 100644
--- a/toonz/sources/toonzqt/fxselection.cpp
+++ b/toonz/sources/toonzqt/fxselection.cpp
@@ -417,6 +417,7 @@ Link FxSelection::getBoundingFxs(SchematicLink *link) {
 Link FxSelection::getBoundingFxs(SchematicPort *inputPort,
                                  SchematicPort *outputPort) {
   Link boundingFxs;
+  if (!inputPort || !outputPort) return boundingFxs;
   FxSchematicNode *inputNode =
       dynamic_cast<FxSchematicNode *>(outputPort->getNode());
   FxSchematicNode *outputNode =
diff --git a/toonz/sources/toonzqt/schematicnode.cpp b/toonz/sources/toonzqt/schematicnode.cpp
index b53c62f..16cd342 100644
--- a/toonz/sources/toonzqt/schematicnode.cpp
+++ b/toonz/sources/toonzqt/schematicnode.cpp
@@ -564,6 +564,12 @@ void SchematicLink::mousePressEvent(QGraphicsSceneMouseEvent *me) {
   QPointF pos              = me->scenePos();
   SchematicPort *startPort = getStartPort();
   SchematicPort *endPort   = getEndPort();
+
+  if (!startPort || !endPort) {
+    me->ignore();
+    return;
+  }
+
   if (startPort && endPort) {
     QRectF startRect = startPort->boundingRect();
     startRect.moveTopLeft(startPort->scenePos());