diff --git a/core/src/main/scala/org/apache/spark/sort/UnsafeSort.scala b/core/src/main/scala/org/apache/spark/sort/UnsafeSort.scala
index 39a712c8c0dfd..259319fb68340 100644
--- a/core/src/main/scala/org/apache/spark/sort/UnsafeSort.scala
+++ b/core/src/main/scala/org/apache/spark/sort/UnsafeSort.scala
@@ -42,7 +42,7 @@ object UnsafeSort {
 
       val outputFile = s"$baseFolder/part$part.dat"
 
-      val os = new BufferedOutputStream(new FileOutputStream(outputFile), 4 * 1024 * 1024)
+      val os = new BufferedOutputStream(new FileOutputStream(outputFile), bufSize)
       val buf = new Array[Byte](100)
       var count = 0
       val arrOffset = BYTE_ARRAY_BASE_OFFSET