diff --git a/demos/main/src/main/java/androidx/media3/demo/main/PlayerActivity.java b/demos/main/src/main/java/androidx/media3/demo/main/PlayerActivity.java
index 1b391bfcdd..155264fb8a 100644
--- a/demos/main/src/main/java/androidx/media3/demo/main/PlayerActivity.java
+++ b/demos/main/src/main/java/androidx/media3/demo/main/PlayerActivity.java
@@ -93,11 +93,11 @@ public class PlayerActivity extends AppCompatActivity
 
   @Nullable private AdsLoader clientSideAdsLoader;
 
-  // TODO: Annotate this and serverSideAdsLoaderState below with @OptIn when it can be applied to
-  // fields (needs http://r.android.com/2004032 to be released into a version of
-  // androidx.annotation:annotation-experimental).
-  @Nullable private ImaServerSideAdInsertionMediaSource.AdsLoader serverSideAdsLoader;
+  @OptIn(markerClass = UnstableApi.class)
+  @Nullable
+  private ImaServerSideAdInsertionMediaSource.AdsLoader serverSideAdsLoader;
 
+  @OptIn(markerClass = UnstableApi.class)
   private ImaServerSideAdInsertionMediaSource.AdsLoader.@MonotonicNonNull State
       serverSideAdsLoaderState;