Problemas com o ConstraintLayout - ImageView 16: 9 margem superior inadequada

Quero criar o seguinte layout usando ConstraintLayout:

Eu uso esta fonte para o layout:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.constraint.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:background="@color/colorAccent">

        <ImageView
            android:id="@+id/imageView"
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:scaleType="centerCrop"
            app:srcCompat="@android:color/darker_gray"
            app:layout_constraintDimensionRatio="h,16:9"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintBottom_toTopOf="@+id/textView1" />

        <TextView
            android:id="@+id/textView1"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="24dp"
            android:layout_marginLeft="16dp"
            android:layout_marginRight="16dp"
            android:text="Title"
            android:textAppearance="@style/TextAppearance.AppCompat.Headline"
            app:layout_constraintTop_toBottomOf="@+id/imageView"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintBottom_toTopOf="@+id/textView2" />

        <TextView
            android:id="@+id/textView2"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:layout_marginLeft="16dp"
            android:layout_marginRight="16dp"
            android:layout_marginBottom="24dp"
            android:text="Subtle"
            app:layout_constraintTop_toBottomOf="@+id/textView1"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintBottom_toBottomOf="parent" />

    </android.support.constraint.ConstraintLayout>
</FrameLayout>

E, infelizmente, obtenha este resultado:

Como você pode ver, há uma margem desnecessária na parte superior do ImageView, embora o layout indique marginTop = 0.

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