Progress dialogue has white background on Lollipop Devices ,

I am migrating my application on Android 5.0 i.e. Lollipop devices , I have problem regarding progress dialog , It work perfectly on pre lollipop devices , but on lollipop it has white background as shown in image

But in pre lollipop devices it is of transparent background

Below is my code :

progress.xml in layout

<?xml version="1.0" encoding="utf-8"?>
   <RelativeLayout xmlns:android="http://ift.tt/nIICcg"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_gravity="center"
   android:background="@android:color/transparent" >


<ProgressBar
        android:id="@+id/progressBar3"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
       android:background="@android:color/transparent"
        android:layout_centerHorizontal="true"

        android:indeterminate="true"
        android:indeterminateDrawable="@drawable/myprogress"
        android:minHeight="48dp" />
   </RelativeLayout>

myprogress.xml in drawable

<shape
    android:shape="oval"
    android:useLevel="false" >
    <size
        android:height="48dip"
        android:width="48dip" />

    <gradient
        android:centerColor="#ff001100"
        android:centerY="0.50"
        android:endColor="#ffffffff"
        android:startColor="#ff000000"
        android:type="sweep"
        android:useLevel="false" />
</shape>

and in Java i am using like this

public ProgressDialog mProgressDialog;

  if (mProgressDialog != null && mProgressDialog.isShowing()) {
            mProgressDialog.cancel();
        }

        mProgressDialog = new ProgressDialog(context);
        mProgressDialog.setCancelable(false);

        mProgressDialog.show();
        mProgressDialog.setContentView(R.layout.progress);