diff --git a/openbis/source/java/ch/systemsx/cisd/openbis/generic/client/web/client/application/ui/property_type/PropertyTypeAssignmentForm.java b/openbis/source/java/ch/systemsx/cisd/openbis/generic/client/web/client/application/ui/property_type/PropertyTypeAssignmentForm.java
index 531989aaabcfc68e259bb5b4bf3cd6dceae8c45c..c74d9e9b5f147d531b89d2b3228c346b54b27b42 100644
--- a/openbis/source/java/ch/systemsx/cisd/openbis/generic/client/web/client/application/ui/property_type/PropertyTypeAssignmentForm.java
+++ b/openbis/source/java/ch/systemsx/cisd/openbis/generic/client/web/client/application/ui/property_type/PropertyTypeAssignmentForm.java
@@ -81,17 +81,17 @@ public final class PropertyTypeAssignmentForm extends LayoutContainer
 
     private ExperimentTypeSelectionWidget experimentTypeSelectionWidget;
 
-    PropertyTypeSelectionWidget propertyTypeSelectionWidget;
+    private PropertyTypeSelectionWidget propertyTypeSelectionWidget;
 
     private Field<?> defaultValueField;
 
     private CheckBox mandatoryCheckbox;
 
-    private InfoBox infoBox;
+    private final InfoBox infoBox;
 
-    private FormPanel formPanel;
+    private final FormPanel formPanel;
 
-    private EntityKind entityKind;
+    private final EntityKind entityKind;
 
     public PropertyTypeAssignmentForm(final IViewContext<ICommonClientServiceAsync> viewContext,
             EntityKind entityKind)