diff --git a/src/PointPlotAction.cpp b/src/PointPlotAction.cpp
index e5c33ab..2425ab6 100644
--- a/src/PointPlotAction.cpp
+++ b/src/PointPlotAction.cpp
@@ -162,6 +162,10 @@ void PointPlotAction::initialize(ScatterplotPlugin* scatterplotPlugin)
     connect(&_opacityAction, &ScalarAction::magnitudeChanged, this, &PointPlotAction::updateScatterPlotWidgetPointOpacityScalars);
     connect(&_opacityAction, &ScalarAction::offsetChanged, this, &PointPlotAction::updateScatterPlotWidgetPointOpacityScalars);
     connect(&_opacityAction, &ScalarAction::sourceSelectionChanged, this, &PointPlotAction::updateScatterPlotWidgetPointOpacityScalars);
+    connect(&_opacityAction.getSourceDatasetPickerAction(), &DatasetPickerAction::datasetPicked, this, [this](Dataset<> picked) -> void {
+        setCurrentPointOpacityDataset(Dataset<DatasetImpl>(picked));
+    });
+
     connect(&_opacityAction, &ScalarAction::sourceDataChanged, this, &PointPlotAction::updateScatterPlotWidgetPointOpacityScalars);
     connect(&_opacityAction, &ScalarAction::scalarRangeChanged, this, &PointPlotAction::updateScatterPlotWidgetPointOpacityScalars);
 }
diff --git a/src/ScalarAction.cpp b/src/ScalarAction.cpp
index 57653e4..24f86b6 100644
--- a/src/ScalarAction.cpp
+++ b/src/ScalarAction.cpp
@@ -29,13 +29,16 @@ ScalarAction::ScalarAction(QObject* parent, const QString& title, const float& m
             if (auto scatterplotPlugin = dynamic_cast<ScatterplotPlugin*>(findPluginAncestor())) {
                 auto positionDataset            = scatterplotPlugin->getPositionDataset();
                 auto scalarSourcePointsDataset  = Dataset<Points>(getCurrentDataset());
-                const auto numScalars           = scalarSourcePointsDataset->getNumPoints();
-                const auto numPositions         = positionDataset->getNumPoints();
 
-                if (numScalars != numPositions) {
-                    emitSourceSelectionChanged = false;
+                if (scalarSourcePointsDataset.isValid() && positionDataset.isValid()) {
+	                const auto numScalars   = scalarSourcePointsDataset->getNumPoints();
+					const auto numPositions = positionDataset->getNumPoints();
 
-                    scatterplotPlugin->addNotification(QString("The number of points in the scalar source dataset does not match the number of points in the position dataset. (numPositions=%1, numScalars:%2)").arg(QString::number(numPositions), QString::number(numScalars)));
+					if (numScalars != numPositions) {
+						emitSourceSelectionChanged = false;
+
+						scatterplotPlugin->addNotification(QString("The number of points in the scalar source dataset does not match the number of points in the position dataset. (numPositions=%1, numScalars:%2)").arg(QString::number(numPositions), QString::number(numScalars)));
+					}
                 }
             }
         } else {