How to pass extra data along with the Intent obtained from GoogleSignInClient.getSignInIntent()?

I need to pass a text-string along with the Google Sign-In Intent, so that I can retrieve it later in the onActivityResult method.

I trigger the GSI account chooser activity with the following code

GoogleSignInOptions googleSignInOptions = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
        .requestIdToken("xxxxxxxxxxxxxxxxxxxxx")
        .requestEmail()
        .build();
final GoogleSignInClient client = GoogleSignIn.getClient(MainActivity.activity, googleSignInOptions);
Intent signInIntent = client.getSignInIntent();

// As extra
signInIntent.putExtra("CALLSTACK_UID", newCallStack.uid);

this.startActivityForResult(signInIntent, RC_SIGN_IN);

and try to retrieve it later via

@Override protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == RC_SIGN_IN) {
        String callstack_uid = data.getStringExtra("CALLSTACK_UID");
        //...
    }
}

data.getStringExtra("CALLSTACK_UID") is always returning null, even when it should be returning a String.

Is my only option here to create a static variable in the activity instead of passing the value through the intent?

from How to pass extra data along with the Intent obtained from GoogleSignInClient.getSignInIntent()?