diff --git a/libraries/session/src/main/java/androidx/media3/session/MediaSession.java b/libraries/session/src/main/java/androidx/media3/session/MediaSession.java
index 2d883a9417..013c3c5c34 100644
--- a/libraries/session/src/main/java/androidx/media3/session/MediaSession.java
+++ b/libraries/session/src/main/java/androidx/media3/session/MediaSession.java
@@ -1651,9 +1651,8 @@ public class MediaSession {
        * session commands}.
        */
       @CanIgnoreReturnValue
-      public AcceptedResultBuilder setCustomLayout(
-          @Nullable ImmutableList<CommandButton> customLayout) {
-        this.customLayout = customLayout;
+      public AcceptedResultBuilder setCustomLayout(@Nullable List<CommandButton> customLayout) {
+        this.customLayout = customLayout == null ? null : ImmutableList.copyOf(customLayout);
         return this;
       }