diff --git a/demos/transformer/src/main/java/com/google/android/exoplayer2/transformerdemo/TransformerActivity.java b/demos/transformer/src/main/java/com/google/android/exoplayer2/transformerdemo/TransformerActivity.java
index eb34fce9fa..8e854517a0 100644
--- a/demos/transformer/src/main/java/com/google/android/exoplayer2/transformerdemo/TransformerActivity.java
+++ b/demos/transformer/src/main/java/com/google/android/exoplayer2/transformerdemo/TransformerActivity.java
@@ -454,7 +454,9 @@ public final class TransformerActivity extends AppCompatActivity {
     "transformationStopwatch",
   })
   private void onTransformationError(TransformationException exception) {
-    transformationStopwatch.stop();
+    if (transformationStopwatch.isRunning()) {
+      transformationStopwatch.stop();
+    }
     informationTextView.setText(R.string.transformation_error);
     progressViewGroup.setVisibility(View.GONE);
     debugFrame.removeAllViews();
diff --git a/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/TransformerInternal.java b/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/TransformerInternal.java
index d8f70a806f..a2aa89c219 100644
--- a/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/TransformerInternal.java
+++ b/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/TransformerInternal.java
@@ -430,8 +430,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
     private void handleTransformationEnded(
         @Nullable TransformationException transformationException) {
-      Util.postOrRun(
-          handler,
+      handler.post(
           () -> {
             @Nullable TransformationException releaseException = null;
             try {