diff --git a/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeMediaSourceFactory.java b/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeMediaSourceFactory.java
index b740de623e..53a0f7eeba 100644
--- a/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeMediaSourceFactory.java
+++ b/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeMediaSourceFactory.java
@@ -27,7 +27,7 @@ import com.google.android.exoplayer2.upstream.LoadErrorHandlingPolicy;
 import com.google.android.exoplayer2.util.Util;
 
 /** Fake {@link MediaSourceFactory} that creates a {@link FakeMediaSource}. */
-public class FakeMediaSourceFactory implements MediaSourceFactory {
+public final class FakeMediaSourceFactory implements MediaSourceFactory {
 
   /** The window UID used by media sources that are created by the factory. */
   public static final Object DEFAULT_WINDOW_UID = new Object();