diff --git a/core/src/main/java/org/apache/spark/shuffle/unsafe/UnsafeShuffleWriter.java b/core/src/main/java/org/apache/spark/shuffle/unsafe/UnsafeShuffleWriter.java
index 22791965dd962..ad7eb04afcd8c 100644
--- a/core/src/main/java/org/apache/spark/shuffle/unsafe/UnsafeShuffleWriter.java
+++ b/core/src/main/java/org/apache/spark/shuffle/unsafe/UnsafeShuffleWriter.java
@@ -36,6 +36,7 @@
 import org.slf4j.LoggerFactory;
 
 import org.apache.spark.*;
+import org.apache.spark.annotation.Private;
 import org.apache.spark.io.CompressionCodec;
 import org.apache.spark.io.CompressionCodec$;
 import org.apache.spark.io.LZFCompressionCodec;
@@ -54,6 +55,7 @@
 import org.apache.spark.unsafe.PlatformDependent;
 import org.apache.spark.unsafe.memory.TaskMemoryManager;
 
+@Private
 public class UnsafeShuffleWriter<K, V> extends ShuffleWriter<K, V> {
 
   private final Logger logger = LoggerFactory.getLogger(UnsafeShuffleWriter.class);
diff --git a/core/src/main/java/org/apache/spark/storage/TimeTrackingOutputStream.java b/core/src/main/java/org/apache/spark/storage/TimeTrackingOutputStream.java
index 0cd3c7d242660..dc2aa30466cc6 100644
--- a/core/src/main/java/org/apache/spark/storage/TimeTrackingOutputStream.java
+++ b/core/src/main/java/org/apache/spark/storage/TimeTrackingOutputStream.java
@@ -20,12 +20,14 @@
 import java.io.IOException;
 import java.io.OutputStream;
 
+import org.apache.spark.annotation.Private;
 import org.apache.spark.executor.ShuffleWriteMetrics;
 
 /**
  * Intercepts write calls and tracks total time spent writing in order to update shuffle write
  * metrics. Not thread safe.
  */
+@Private
 public final class TimeTrackingOutputStream extends OutputStream {
 
   private final ShuffleWriteMetrics writeMetrics;