diff --git a/src/helma/framework/core/SkinFile.java b/src/helma/framework/core/SkinFile.java
index cd00bad4..a7709385 100644
--- a/src/helma/framework/core/SkinFile.java
+++ b/src/helma/framework/core/SkinFile.java
@@ -13,7 +13,7 @@ import helma.util.Updatable;
  */
 
 
-public class SkinFile implements Updatable {
+public final class SkinFile implements Updatable {
 
     String name;
     Prototype prototype;
diff --git a/src/helma/objectmodel/db/DbMapping.java b/src/helma/objectmodel/db/DbMapping.java
index 287e6760..b89731ed 100644
--- a/src/helma/objectmodel/db/DbMapping.java
+++ b/src/helma/objectmodel/db/DbMapping.java
@@ -19,7 +19,7 @@ import com.workingdogs.village.*;
   * Database row bindings which are represented by instances of the Relation class.
   */
   
-public class DbMapping implements Updatable {
+public final class DbMapping implements Updatable {
 
     // DbMappings belong to an application
     Application app;
diff --git a/src/helma/objectmodel/db/Relation.java b/src/helma/objectmodel/db/Relation.java
index 6050ac7c..57c514fa 100644
--- a/src/helma/objectmodel/db/Relation.java
+++ b/src/helma/objectmodel/db/Relation.java
@@ -14,7 +14,7 @@ import java.sql.SQLException;
  *  relational database table. This can be either a scalar property (string, date, number etc.)
  *  or a reference to one or more other objects.
  */
-public class Relation {
+public final class Relation {
 
     // these constants define different type of property-to-db-mappings