Android persistent bottom sheet initial visibility

I'm trying to implement a persistent bottom sheet in my layout - one that cannot be completely hidden, but always peeks from the bottom and can be expanded to full height. This is my layout:

<android.support.design.widget.CoordinatorLayout
    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.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:orientation="vertical">

        <!-- main content -->

    </LinearLayout>

    <LinearLayout
        android:id="@+id/layoutBottomSheet"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center|bottom"
        android:background="@drawable/custom_background"
        android:clipToPadding="false"
        android:gravity="center_horizontal"
        android:orientation="vertical"
        app:behavior_hideable="false"
        app:behavior_peekHeight="50dp"
        app:layout_behavior="@string/bottom_sheet_behavior">

        <!-- bottom sheet content -->

    </LinearLayout>

</android.support.design.widget.CoordinatorLayout>

What I expect to happen is for the bottom sheet to be visible and collapsed as soon as I land on the screen, but it's not - it's hidden. I can get it to show up by calling bottomSheetBehaviour.setState(BottomSheetBehavior.STATE_EXPANDED) in onCreate(). This, curiously, only expands it slightly - more than the peek height specified but less than the full height it should take up. After it appears in this state I can drag it up and down to where it should be and it works fine. The problem is the initial landing on the screen is messed up.

I'm sure there's a way I can get this working so the Bottom Sheet initially appears at it's peek height. Any ideas?