diff --git a/scm-webapp/src/main/java/sonia/scm/ClassOverride.java b/scm-webapp/src/main/java/sonia/scm/ClassOverride.java
index 4d64a07d3b..a9d28c7fdc 100644
--- a/scm-webapp/src/main/java/sonia/scm/ClassOverride.java
+++ b/scm-webapp/src/main/java/sonia/scm/ClassOverride.java
@@ -41,7 +41,7 @@ import javax.xml.bind.annotation.XmlAccessorType;
  * @author Sebastian Sdorra
  */
 @XmlAccessorType(XmlAccessType.FIELD)
-public class ClassOverride
+public class ClassOverride implements Validateable
 {
 
   /**
@@ -66,6 +66,18 @@ public class ClassOverride
     return to;
   }
 
+  /**
+   * Method description
+   *
+   *
+   * @return
+   */
+  @Override
+  public boolean isValid()
+  {
+    return (bind != null) && (to != null);
+  }
+
   //~--- set methods ----------------------------------------------------------
 
   /**
diff --git a/scm-webapp/src/main/java/sonia/scm/ClassOverrides.java b/scm-webapp/src/main/java/sonia/scm/ClassOverrides.java
index d82bb62310..b4560f0275 100644
--- a/scm-webapp/src/main/java/sonia/scm/ClassOverrides.java
+++ b/scm-webapp/src/main/java/sonia/scm/ClassOverrides.java
@@ -36,6 +36,8 @@ package sonia.scm;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import sonia.scm.util.AssertUtil;
+
 //~--- JDK imports ------------------------------------------------------------
 
 import java.io.IOException;
@@ -157,7 +159,19 @@ public class ClassOverrides implements Iterable<ClassOverride>
    */
   public void append(ClassOverrides overrides)
   {
-    getOverrides().addAll(overrides.getOverrides());
+    AssertUtil.assertIsNotNull(overrides);
+
+    for (ClassOverride co : overrides)
+    {
+      if (co.isValid())
+      {
+        getOverrides().add(co);
+      }
+      else if (logger.isWarnEnabled())
+      {
+        logger.warn("could not append ClassOverride, because it is not valid");
+      }
+    }
   }
 
   /**