Flutter - Hero widget child Image url from Firebase

I am trying to create a Hero widget which has a child Image.network()

Hero(
 tag: 'headerView',
 transitionOnUserGestures: true,
 child: Image.network(
   headerPhoto,
   fit: BoxFit.cover,
 ),
)

The image url -headerPhoto- is being fetched from Firestore asynchronously, therefore, I assume I have to put this Hero widget inside a FutureBuilder.

FutureBuilder(
  builder: (context, snapshot) {
  ...
    if (snapshot.connectionState == ConnectionState.done) {
      if (snapshot.hasData) {
        String headerPhoto = snapshot.data['headerPhoto'];
        return Scaffold(
          body:GestureDetector(
            onTap: () {
              _showPage('headerView', headerPhoto);
            },
            child: Hero(
              tag: 'headerView',
              transitionOnUserGestures: true,
              child: Image.network(
                headerPhoto,
                width: MediaQuery.of(context).size.width,
                fit: BoxFit.cover,
              ),
            ),
          ),
        )
      } 
    }
    ...
  },
  future: _fetchHeaderPhoto(userData),
);

When I use Hero widget inside the FutureBuilder like above, first animation works like it should. But when I navigate back from PageView -which only have Hero widget in it- the animation does not work. On the other hand, while I was trying Hero widget with hardcoded strings like:

Hero(
  tag: 'headerView',
  transitionOnUserGestures: true,
  child: Image.network(
    'https://picsum.photos/200/300',
    fit: BoxFit.cover,
  ),
)

First animation and second animation both worked perfectly. Is this problem occurs because I use FutureBuilder? If it isn't what is the problem?

Thanks in advance.