how to set a value with span tag capyabara : Does anyone know how to set a value to span tag?

I tried using element.set or element.send_keys, they only selected the targeted element without modifing the previous value

<div data-offset-key="bbpvo-0-0" class="_1mf _1mj"><span data-offset-key="bbpvo-0-0"><span data-text="true">aa</span></span></div>

html snippet as above, I want to set aa to bb. can anyone help me out? thanks