How to change UI Button label in controller?

It's sound simple but I'm going nuts here, and I'm simply trying to change the label name in the controller.js file

Here is what I'm doing here, any help?

Component:

<ui:button aura:id = "Btn1" label="Get Password" class="slds-button slds-button_brand" press="{!c.handleClick}" />

Controller JS:

var currentBoatTypeChoice = component.find("Btn1");//.get("v.label");
currentBoatTypeChoice.set('v.label','New Label');