diff --git a/src/src/main/scala/org/alitouka/spark/dbscan/spatial/Box.scala b/src/src/main/scala/org/alitouka/spark/dbscan/spatial/Box.scala
index d46a71b..2128635 100644
--- a/src/src/main/scala/org/alitouka/spark/dbscan/spatial/Box.scala
+++ b/src/src/main/scala/org/alitouka/spark/dbscan/spatial/Box.scala
@@ -9,7 +9,7 @@ import org.alitouka.spark.dbscan.util.math.DoubleComparisonOperations._
   * @param boxId A unique identifier of this box
   * @param partitionId Identifier of a data set partition which corresponds to this box
   */
-private [dbscan] class Box (val bounds: Array[BoundsInOneDimension], val boxId: BoxId = 0, val partitionId: Int = -1, var adjacentBoxes: List[Box] = Nil)
+private [dbscan] class Box (val bounds: Array[BoundsInOneDimension], val boxId: BoxId = 0, val partitionId: Int = -1, @transient var adjacentBoxes: List[Box] = Nil)
   extends Serializable with Ordered[Box] {
 
   val centerPoint = calculateCenter (bounds)
@@ -133,4 +133,4 @@ object Box {
     val newBounds = centerPoint.coordinates.map ( c => new BoundsInOneDimension(c, c, true) ).toArray
     new Box (newBounds).extendBySizeOfOtherBox(size)
   }
-}
\ No newline at end of file
+}