diff --git a/GUI/Views/SampleDesigner/SampleViewFactory.cpp b/GUI/Views/SampleDesigner/SampleViewFactory.cpp
index a6a800ed8e30838e26455b3a27115b0b2a088afe..ba6077a9b95a4abf377ce3cc0838475576753ab3 100644
--- a/GUI/Views/SampleDesigner/SampleViewFactory.cpp
+++ b/GUI/Views/SampleDesigner/SampleViewFactory.cpp
@@ -32,28 +32,31 @@
 #include "GUI/Views/SampleDesigner/ParticleView.h"
 #include "GUI/Views/SampleDesigner/TransformationView.h"
 
-QStringList SampleViewFactory::m_valid_item_types = {MultiLayerItem::M_TYPE,
-                                                     LayerItem::M_TYPE,
-                                                     ParticleLayoutItem::M_TYPE,
-                                                     ParticleItem::M_TYPE,
-                                                     TransformationItem::M_TYPE,
-                                                     ParticleCoreShellItem::M_TYPE,
-                                                     ParticleCompositionItem::M_TYPE,
-                                                     MesoCrystalItem::M_TYPE,
-                                                     Interference1DLatticeItem::M_TYPE,
-                                                     Interference2DLatticeItem::M_TYPE,
-                                                     Interference2DParaCrystalItem::M_TYPE,
-                                                     InterferenceFinite2DLatticeItem::M_TYPE,
-                                                     InterferenceHardDiskItem::M_TYPE,
-                                                     InterferenceRadialParaCrystalItem::M_TYPE};
+namespace {
+
+QStringList valid_item_types = {MultiLayerItem::M_TYPE,
+    LayerItem::M_TYPE,
+    ParticleLayoutItem::M_TYPE,
+    ParticleItem::M_TYPE,
+    TransformationItem::M_TYPE,
+    ParticleCoreShellItem::M_TYPE,
+    ParticleCompositionItem::M_TYPE,
+    MesoCrystalItem::M_TYPE,
+    Interference1DLatticeItem::M_TYPE,
+    Interference2DLatticeItem::M_TYPE,
+    Interference2DParaCrystalItem::M_TYPE,
+    InterferenceFinite2DLatticeItem::M_TYPE,
+    InterferenceHardDiskItem::M_TYPE,
+    InterferenceRadialParaCrystalItem::M_TYPE};
+
+} // namespace
 
 bool SampleViewFactory::isValidType(const QString& model_type)
 {
     if (model_type.startsWith("FormFactor")) {
         return true;
-    } else {
-        return m_valid_item_types.contains(model_type);
     }
+    return valid_item_types.contains(model_type);
 }
 
 IView* SampleViewFactory::createSampleView(const QString& model_type)
diff --git a/GUI/Views/SampleDesigner/SampleViewFactory.h b/GUI/Views/SampleDesigner/SampleViewFactory.h
index 9b4a48dd81412e48653a7880d1e60c415b5ae3bd..744ef0f3127cee7d8e0df893505d0f370ccfbe54 100644
--- a/GUI/Views/SampleDesigner/SampleViewFactory.h
+++ b/GUI/Views/SampleDesigner/SampleViewFactory.h
@@ -23,9 +23,6 @@ class SampleViewFactory {
 public:
     static bool isValidType(const QString& model_type);
     static IView* createSampleView(const QString& model_type);
-
-private:
-    static QStringList m_valid_item_types;
 };
 
 #endif // BORNAGAIN_GUI_VIEWS_SAMPLEDESIGNER_SAMPLEVIEWFACTORY_H