Apps a problam with TableRow height

[Piece_Of_Meat]

I have a tablelayout and i want the second row to be 15% of the height and the first row to be 85% of the height, so i use weights and it's work just fine.
But when i put ImageButton on the second row the height of the second row becomes bigger then it was before. The height of the imageButton is no more then the 15% of the total height so i don`t understand why it happenes.
Here is my xml code:

<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:weightSum="100" >

    <TableRow
        android:id="@+id/tableRow1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="85" >
    </TableRow>

    <TableRow
        android:id="@+id/tableRow2"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="15" >

        <ImageButton
            android:id="@+id/ibTakePic"
            android:layout_width="75dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:src="@drawable/profile" />
    </TableRow>

</TableLayout>