diff --git a/src/main/scala/org/pmml4s/data/DataVal.scala b/src/main/scala/org/pmml4s/data/DataVal.scala
index 4ecf271..e90a0a8 100644
--- a/src/main/scala/org/pmml4s/data/DataVal.scala
+++ b/src/main/scala/org/pmml4s/data/DataVal.scala
@@ -21,10 +21,9 @@ import org.pmml4s.util.StringUtils
 
 import java.text.DecimalFormat
 import java.util.Date
-import scala.collection.immutable.Iterable
 import scala.reflect.ClassTag
 
-sealed trait DataVal {
+sealed trait DataVal extends Serializable {
   def isMissing: Boolean = false
 
   def nonMissing: Boolean = true