diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/ads/AdsMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/ads/AdsMediaSource.java
index a10bc9019b..6061b014a7 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/ads/AdsMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/ads/AdsMediaSource.java
@@ -331,9 +331,6 @@ public final class AdsMediaSource extends CompositeMediaSource<MediaPeriodId> {
       boolean isTopLevelSource,
       @Nullable TransferListener mediaTransferListener) {
     super.prepareSourceInternal(player, isTopLevelSource, mediaTransferListener);
-    Assertions.checkArgument(
-        isTopLevelSource,
-        "AdsMediaSource must be the top-level source used to prepare the player.");
     final ComponentListener componentListener = new ComponentListener();
     this.componentListener = componentListener;
     prepareChildSource(DUMMY_CONTENT_MEDIA_PERIOD_ID, contentMediaSource);
@@ -444,6 +441,7 @@ public final class AdsMediaSource extends CompositeMediaSource<MediaPeriodId> {
   }
 
   private void onContentSourceInfoRefreshed(Timeline timeline, Object manifest) {
+    Assertions.checkArgument(timeline.getPeriodCount() == 1);
     contentTimeline = timeline;
     contentManifest = manifest;
     maybeUpdateSourceInfo();