diff --git a/demos/transformer/src/main/java/androidx/media3/demo/transformer/ConfigurationActivity.java b/demos/transformer/src/main/java/androidx/media3/demo/transformer/ConfigurationActivity.java
index 4d41a588a5..aab9821902 100644
--- a/demos/transformer/src/main/java/androidx/media3/demo/transformer/ConfigurationActivity.java
+++ b/demos/transformer/src/main/java/androidx/media3/demo/transformer/ConfigurationActivity.java
@@ -302,6 +302,18 @@ public final class ConfigurationActivity extends AppCompatActivity {
     abortSlowExportCheckBox = findViewById(R.id.abort_slow_export_checkbox);
     useMedia3Muxer = findViewById(R.id.use_media3_muxer_checkbox);
     produceFragmentedMp4CheckBox = findViewById(R.id.produce_fragmented_mp4_checkbox);
+    useMedia3Muxer.setOnCheckedChangeListener(
+        (buttonView, isChecked) -> {
+          if (!isChecked) {
+            produceFragmentedMp4CheckBox.setChecked(false);
+          }
+        });
+    produceFragmentedMp4CheckBox.setOnCheckedChangeListener(
+        (buttonView, isChecked) -> {
+          if (isChecked) {
+            useMedia3Muxer.setChecked(true);
+          }
+        });
 
     ArrayAdapter<String> hdrModeAdapter =
         new ArrayAdapter<>(/* context= */ this, R.layout.spinner_item);
diff --git a/demos/transformer/src/main/java/androidx/media3/demo/transformer/TransformerActivity.java b/demos/transformer/src/main/java/androidx/media3/demo/transformer/TransformerActivity.java
index a006971fc3..95f2f94849 100644
--- a/demos/transformer/src/main/java/androidx/media3/demo/transformer/TransformerActivity.java
+++ b/demos/transformer/src/main/java/androidx/media3/demo/transformer/TransformerActivity.java
@@ -84,10 +84,8 @@ import androidx.media3.exoplayer.DefaultLoadControl;
 import androidx.media3.exoplayer.ExoPlayer;
 import androidx.media3.exoplayer.audio.SilenceSkippingAudioProcessor;
 import androidx.media3.exoplayer.util.DebugTextViewHelper;
-import androidx.media3.muxer.Muxer;
 import androidx.media3.transformer.Composition;
 import androidx.media3.transformer.DefaultEncoderFactory;
-import androidx.media3.transformer.DefaultMuxer;
 import androidx.media3.transformer.EditedMediaItem;
 import androidx.media3.transformer.EditedMediaItemSequence;
 import androidx.media3.transformer.Effects;
@@ -325,14 +323,13 @@ public final class TransformerActivity extends AppCompatActivity {
         transformerBuilder.setMaxDelayBetweenMuxerSamplesMs(C.TIME_UNSET);
       }
 
-      Muxer.Factory muxerFactory = new DefaultMuxer.Factory();
       if (bundle.getBoolean(ConfigurationActivity.USE_MEDIA3_MUXER)) {
-        muxerFactory = new InAppMuxer.Factory.Builder().build();
+        transformerBuilder.setMuxerFactory(
+            new InAppMuxer.Factory.Builder()
+                .setOutputFragmentedMp4(
+                    bundle.getBoolean(ConfigurationActivity.PRODUCE_FRAGMENTED_MP4))
+                .build());
       }
-      if (bundle.getBoolean(ConfigurationActivity.PRODUCE_FRAGMENTED_MP4)) {
-        muxerFactory = new InAppMuxer.Factory.Builder().setOutputFragmentedMp4(true).build();
-      }
-      transformerBuilder.setMuxerFactory(muxerFactory);
 
       if (bundle.getBoolean(ConfigurationActivity.ENABLE_DEBUG_PREVIEW)) {
         transformerBuilder.setDebugViewProvider(new DemoDebugViewProvider());