diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/chunk/Chunk.java b/library/core/src/main/java/com/google/android/exoplayer2/source/chunk/Chunk.java
index f9e58e2353..25877d12d6 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/chunk/Chunk.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/chunk/Chunk.java
@@ -46,12 +46,13 @@ public abstract class Chunk implements Loadable {
   public final Format trackFormat;
   /**
    * One of the {@link C} {@code SELECTION_REASON_*} constants if the chunk belongs to a track.
-   * {@link C#SELECTION_REASON_UNKNOWN} if the chunk does not belong to a track.
+   * {@link C#SELECTION_REASON_UNKNOWN} if the chunk does not belong to a track, or if the selection
+   * reason is unknown.
    */
   public final int trackSelectionReason;
   /**
    * Optional data associated with the selection of the track to which this chunk belongs. Null if
-   * the chunk does not belong to a track.
+   * the chunk does not belong to a track, or if there is no associated track selection data.
    */
   @Nullable public final Object trackSelectionData;
   /**
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/chunk/ContainerMediaChunk.java b/library/core/src/main/java/com/google/android/exoplayer2/source/chunk/ContainerMediaChunk.java
index 6af85c07ac..5fa85a33e3 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/chunk/ContainerMediaChunk.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/chunk/ContainerMediaChunk.java
@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.source.chunk;
 
+import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.extractor.DefaultExtractorInput;
@@ -67,7 +68,7 @@ public class ContainerMediaChunk extends BaseMediaChunk {
       DataSpec dataSpec,
       Format trackFormat,
       int trackSelectionReason,
-      Object trackSelectionData,
+      @Nullable Object trackSelectionData,
       long startTimeUs,
       long endTimeUs,
       long clippedStartTimeUs,
diff --git a/library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/DefaultSsChunkSource.java b/library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/DefaultSsChunkSource.java
index 0ddbebfd17..5ce2e6a1c5 100644
--- a/library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/DefaultSsChunkSource.java
+++ b/library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/DefaultSsChunkSource.java
@@ -38,6 +38,7 @@ import com.google.android.exoplayer2.upstream.DataSource;
 import com.google.android.exoplayer2.upstream.DataSpec;
 import com.google.android.exoplayer2.upstream.LoaderErrorThrower;
 import com.google.android.exoplayer2.upstream.TransferListener;
+import com.google.android.exoplayer2.util.Assertions;
 import java.io.IOException;
 import java.util.List;
 
@@ -80,7 +81,7 @@ public class DefaultSsChunkSource implements SsChunkSource {
   private SsManifest manifest;
   private int currentManifestChunkOffset;
 
-  private IOException fatalError;
+  @Nullable private IOException fatalError;
 
   /**
    * @param manifestLoaderErrorThrower Throws errors affecting loading of manifests.
@@ -106,8 +107,11 @@ public class DefaultSsChunkSource implements SsChunkSource {
     for (int i = 0; i < extractorWrappers.length; i++) {
       int manifestTrackIndex = trackSelection.getIndexInTrackGroup(i);
       Format format = streamElement.formats[manifestTrackIndex];
+      @Nullable
       TrackEncryptionBox[] trackEncryptionBoxes =
-          format.drmInitData != null ? manifest.protectionElement.trackEncryptionBoxes : null;
+          format.drmInitData != null
+              ? Assertions.checkNotNull(manifest.protectionElement).trackEncryptionBoxes
+              : null;
       int nalUnitLengthFieldLength = streamElement.type == C.TRACK_TYPE_VIDEO ? 4 : 0;
       Track track = new Track(manifestTrackIndex, streamElement.type, streamElement.timescale,
           C.TIME_UNSET, manifest.durationUs, format, Track.TRANSFORMATION_NONE,
@@ -277,7 +281,7 @@ public class DefaultSsChunkSource implements SsChunkSource {
       long chunkEndTimeUs,
       long chunkSeekTimeUs,
       int trackSelectionReason,
-      Object trackSelectionData,
+      @Nullable Object trackSelectionData,
       ChunkExtractorWrapper extractorWrapper) {
     DataSpec dataSpec = new DataSpec(uri);
     // In SmoothStreaming each chunk contains sample timestamps relative to the start of the chunk.