After upgrade to Laravel 5.1, session flash data persisting across redirects indefinitely

After upgrading from Laravel 4.2 to 5.0, then 5.1, my app has a weird issue. Session data that is stored through redirect('route/to')->with() persists indefinitely. The only way to clear it is by truncating my database session table. Perhaps related as well, redirect('route/to')->withInput() also causes the form to persistently show the same set of values.

I'm still getting up to speed with changes from 4.2 to 5.0 to 5.1...but anyone knows what is the cause of this issue?

Thanks.

via Chebli Mohamed