Props input classes expected string go Array

[Aslam97]

vue.common.dev.js?4650:630 [Vue warn]: Invalid prop: type check failed for prop "inputClasses". Expected String with value "resources-js-auth-views-partials-_otp__otp_input resources-js-auth-views-partials-_otp__error", got Array

code

:input-classes="[$style.otp_input, [$style.error]: otpError ]"

I solve this by just put the condition inside computed

 otpInputClass() {
   return `${this.$style.otp_input} ${this.otpError ? this.$style.error : ''}`;
 }

but again it is good if i can do conditional without using computed

thanks