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://schemas.android.com/apk/res/android"

   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>

<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>

public ProgressDialog mProgressDialog;



  if (mProgressDialog != null && mProgressDialog.isShowing()) {

            mProgressDialog.cancel();

        }



        mProgressDialog = new ProgressDialog(context);

        mProgressDialog.setCancelable(false);



        mProgressDialog.show();

        mProgressDialog.setContentView(R.layout.progress);