diff --git a/src/gui/processing/qgsprocessingtoolboxtreeview.cpp b/src/gui/processing/qgsprocessingtoolboxtreeview.cpp
index 9c34bf176cf9..47791dd3e869 100644
--- a/src/gui/processing/qgsprocessingtoolboxtreeview.cpp
+++ b/src/gui/processing/qgsprocessingtoolboxtreeview.cpp
@@ -31,7 +31,7 @@ QgsProcessingToolboxTreeView::QgsProcessingToolboxTreeView( QWidget *parent,
 void QgsProcessingToolboxTreeView::setRegistry( QgsProcessingRegistry *registry, QgsProcessingRecentAlgorithmLog *recentLog )
 {
   QgsProcessingToolboxProxyModel *newModel = new QgsProcessingToolboxProxyModel( this, registry, recentLog );
-  mToolboxModel = mModel->toolboxModel();
+  mToolboxModel = newModel->toolboxModel();
   setModel( newModel );
   mModel->deleteLater();
   mModel = newModel;
diff --git a/src/gui/processing/qgsprocessingtoolboxtreeview.h b/src/gui/processing/qgsprocessingtoolboxtreeview.h
index 2c213ecfcfc3..fdee7cc0e93f 100644
--- a/src/gui/processing/qgsprocessingtoolboxtreeview.h
+++ b/src/gui/processing/qgsprocessingtoolboxtreeview.h
@@ -109,6 +109,8 @@ class GUI_EXPORT QgsProcessingToolboxTreeView : public QTreeView
      */
     QModelIndex findFirstVisibleAlgorithm( const QModelIndex &parent );
 
+    friend class TestQgsProcessingModel;
+
 };
 
 ///@endcond
diff --git a/tests/src/gui/testqgsprocessingmodel.cpp b/tests/src/gui/testqgsprocessingmodel.cpp
index c6bea38d58d1..b7a6ebe5531d 100644
--- a/tests/src/gui/testqgsprocessingmodel.cpp
+++ b/tests/src/gui/testqgsprocessingmodel.cpp
@@ -154,6 +154,10 @@ void TestQgsProcessingModel::testModel()
   QVERIFY( !model.providerForIndex( model.index( 0, 0, QModelIndex() ) ) );
   QVERIFY( !model.providerForIndex( model.index( 1, 0, QModelIndex() ) ) );
   QVERIFY( !model.indexForProvider( nullptr ).isValid() );
+  QVERIFY( model.index2node( QModelIndex() ) ); // root node
+  QCOMPARE( model.index2node( QModelIndex() )->nodeType(), QgsProcessingToolboxModelNode::NodeGroup );
+  QVERIFY( model.index2node( model.index( -1, 0, QModelIndex() ) ) ); // root node
+  QCOMPARE( model.index2node( QModelIndex() ), model.index2node( model.index( -1, 0, QModelIndex() ) ) );
 
   // add a provider
   DummyProvider *p1 = new DummyProvider( "p1", "provider1" );
@@ -559,6 +563,11 @@ void TestQgsProcessingModel::testView()
   QgsProcessingRecentAlgorithmLog recentLog;
   QgsProcessingToolboxTreeView view( nullptr, &registry, &recentLog );
 
+  // Check view model consistency
+  QVERIFY( view.mModel );
+  QVERIFY( view.mToolboxModel );
+  QCOMPARE( view.mModel->toolboxModel(), view.mToolboxModel );
+
   QVERIFY( !view.algorithmForIndex( QModelIndex() ) );
 
   // add a provider
@@ -636,6 +645,13 @@ void TestQgsProcessingModel::testView()
   // but if it doesn't remove the selected one, that algorithm should not be deselected
   view.setFilterString( QStringLiteral( "a" ) );
   QCOMPARE( view.selectedAlgorithm()->id(), QStringLiteral( "p2:a1" ) );
+
+  // Check view model consistency after resetting registry
+  view.setRegistry( &registry );
+  QVERIFY( view.mModel );
+  QVERIFY( view.mToolboxModel );
+  QCOMPARE( view.mModel->toolboxModel(), view.mToolboxModel );
+
 }
 
 QGSTEST_MAIN( TestQgsProcessingModel )