LinearLayout Inside of ScrollView doesn't expand

For some reason I can't horizontally scroll through my linear layout...

I tried this solution and it didn't work: LinearLayout not expanding inside a ScrollView

Is there something else that I'm missing?

Here is my code:

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fadingEdge="horizontal"
    android:scrollbars="horizontal"
    android:fillViewport="true" >

 <LinearLayout
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"
     android:orientation="horizontal"
     android:scrollbarStyle="insideOverlay"
     android:scrollbars="horizontal" >

     <ImageButton
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:background="@drawable/ventuscartoon" >

     </ImageButton>

     <ImageButton
         android:id="@+id/imageButton1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:src="@drawable/eincartoon" />

     <ImageButton
         android:id="@+id/imageButton3"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:src="@drawable/ventuscartoon" />

     <ImageButton
         android:id="@+id/imageButton2"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:src="@drawable/ventuscartoon" />

</LinearLayout>

</ScrollView>

Thanks!