ios - How to prevent style-change on login-button -

i using facebook's own api give users alternative login-method in app. i'm using own fbsdkloginbutton so.

when user enters login-view in app, looks this:

when user clicks button, open facebook-app (or browser, if app isn't available), , prompt user log in. after successful login, should return app. does. problem is, facebook-button looks this:

i don't know why or how prevent it.. it's not end of world me, view disappear right after this, kinda annoying.

i have not done button. dragged uibutton storyboard, , set subclass of fbsdkloginbutton. in code, have set btnfacebooklogin.delegate = self, implementing delegates in loginviewcontroller.h.

i tried adding btnfacebooklogin.clipstobounds = yes no avail. backgroundcolor of entire button nothing. believe has button's layer, i'm reluctant search through layers , find change something. there has reason this?

to clear, want style same, instead of changing transparent text and.. 'discoloration'..

update

actually, result changes when adding clipstobounds = yes button. following result:

the image positioned , sized using constraints in storyboard. maybe has it.. white square behind original result might resemble width button would've had if used on <=iphone 5s.. is, however, strange it's not aligned properly.. it's not centered.

make sure uibutton property showstouchwhenhighlighted set false. if not work make sure property adjustsimagewhenhighlighted set false.