diff --git a/framework/src/main/java/de/hsadmin/module/impl/AbstractProperty.java b/framework/src/main/java/de/hsadmin/module/impl/AbstractProperty.java
index 99de592..a8e0ab2 100644
--- a/framework/src/main/java/de/hsadmin/module/impl/AbstractProperty.java
+++ b/framework/src/main/java/de/hsadmin/module/impl/AbstractProperty.java
@@ -22,7 +22,8 @@ public abstract class AbstractProperty<T> implements Property<T> {
 	
 	private PersistentObjectMapper<T> persistentObjectMapper;
 	private ParameterMapMapper<T> parameterMapMapper;
-	private boolean undefinedValue;
+	
+	protected boolean undefinedValue;
 
 	public AbstractProperty(
 			final ValueObject owner, 
diff --git a/framework/src/main/java/de/hsadmin/module/property/StringSetProperty.java b/framework/src/main/java/de/hsadmin/module/property/StringSetProperty.java
index a393a14..7477abc 100644
--- a/framework/src/main/java/de/hsadmin/module/property/StringSetProperty.java
+++ b/framework/src/main/java/de/hsadmin/module/property/StringSetProperty.java
@@ -37,6 +37,7 @@ public class StringSetProperty extends AbstractProperty<StringSet> {
 	
 	@Override
 	public void setValue(final StringSet value) throws TechnicalException {
+		undefinedValue = false;
 		ReflectionUtil.invokeSetter(owningVO, getName(), value.getStrings());
 	}