How do I keep the saved progress when updating a game?

My game is already published in Google Play, but if I install it in my Android mobile, play it and save some progress (with local webstorage) and later the game is updated via Google Play, the saved progress is lost when I open the newly installed version. Is this normal? Is there any way to avoid this?

Thanks in advance!

I think its normal, it overwrites the current progress ! Even my game does the same .