diff --git a/src/main/scala/ALSAlgorithm.scala b/src/main/scala/ALSAlgorithm.scala
index f99e525..bc2b7b1 100644
--- a/src/main/scala/ALSAlgorithm.scala
+++ b/src/main/scala/ALSAlgorithm.scala
@@ -84,10 +84,10 @@
       // index. Convert it to String ID for returning PredictedResult
       val itemScores = model.recommendProducts(userInt, query.num)
         .map (r => ItemScore(itemIntStringMap(r.product), r.rating))
-      new PredictedResult(itemScores)
+      PredictedResult(itemScores)
     }.getOrElse{
       logger.info(s"No prediction for unknown user ${query.user}.")
-      new PredictedResult(Array.empty)
+      PredictedResult(Array.empty)
     }
   }
 
diff --git a/src/main/scala/Engine.scala b/src/main/scala/Engine.scala
index bbec828..71e09bf 100644
--- a/src/main/scala/Engine.scala
+++ b/src/main/scala/Engine.scala
@@ -6,20 +6,20 @@
 case class Query(
   user: String,
   num: Int
-) extends Serializable
+)
 
 case class PredictedResult(
   itemScores: Array[ItemScore]
-) extends Serializable
+)
 
 case class ActualResult(
   ratings: Array[Rating]
-) extends Serializable
+)
 
 case class ItemScore(
   item: String,
   score: Double
-) extends Serializable
+)
 
 object RecommendationEngine extends EngineFactory {
   def apply() = {