diff --git a/core/src/main/scala/org/apache/spark/storage/memory/MemoryStore.scala b/core/src/main/scala/org/apache/spark/storage/memory/MemoryStore.scala
index 00475288564f1a8e023d678adc2d2248d6126494..9b636338ff2ed6e96d1ef7d55d0dc254329561d9 100644
--- a/core/src/main/scala/org/apache/spark/storage/memory/MemoryStore.scala
+++ b/core/src/main/scala/org/apache/spark/storage/memory/MemoryStore.scala
@@ -23,7 +23,7 @@ import java.util.LinkedHashMap
 
 import scala.collection.mutable
 import scala.collection.mutable.ArrayBuffer
-import scala.collection.mutable.SortedMap
+import scala.collection.SortedMap
 import scala.reflect.ClassTag
 
 import com.google.common.io.ByteStreams
@@ -90,8 +90,8 @@ private[spark] class MemoryStore(
   // acquiring or releasing unroll memory, must be synchronized on `memoryManager`!
 
   private class OurBlockIdAndSizeType(
-      blockId: BlockId,
-      size: Long) extends Ordering[OurBlockIdAndSizeType] {
+      private var blockId: BlockId,
+      private var size: Long) extends Ordering[OurBlockIdAndSizeType] {
     def compare(other: OurBlockIdAndSizeType): Int = this.size compare other.size
   }