diff --git a/core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleReader.scala b/core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleReader.scala
index 0f315b85bfca6..ea8aa346cd9f3 100644
--- a/core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleReader.scala
+++ b/core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleReader.scala
@@ -38,7 +38,7 @@ private[spark] class HashShuffleReader[K, C](
   /** Read the combined key-values for this reduce task */
   override def read(): Iterator[Product2[K, C]] = {
     val blockStreams = BlockStoreShuffleFetcher.fetchBlockStreams(
-                       handle.shuffleId, startPartition, context)
+                         handle.shuffleId, startPartition, context)
 
     // Wrap the streams for compression based on configuration
     val wrappedStreams = blockStreams.map { case (blockId, inputStream) =>
diff --git a/core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala b/core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala
index 3758a758943d4..771194225af2f 100644
--- a/core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala
+++ b/core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala
@@ -21,7 +21,7 @@ import java.io.InputStream
 import java.util.concurrent.LinkedBlockingQueue
 
 import scala.collection.mutable
-import scala.collection.mutable.ArrayBuffer
+import scala.collection.mutable.{ArrayBuffer, HashSet}
 import scala.util.{Failure, Try}
 
 import org.apache.spark.network.buffer.ManagedBuffer
@@ -78,7 +78,7 @@ final class ShuffleBlockFetcherIterator(
   private[this] val localBlocks = new ArrayBuffer[BlockId]()
 
   /** Remote blocks to fetch, excluding zero-sized blocks. */
-  private[this] val remoteBlocks = new mutable.HashSet[BlockId]()
+  private[this] val remoteBlocks = new HashSet[BlockId]()
 
   /**
    * A queue to hold our results. This turns the asynchronous model provided by