Require Input Claims From JWT From RelyingParty in Azure AD B2C

I'm sending claims to B2C via a JWT following the WingTig Games demo code. How do I require claim(s) to sent by the relying party? And if they are not sent, prevent the sign-up process? And provide my own error message to the user.

I tried adding required in my leaf policy in the RelyingParty node but it let me through. I tried adding required to my TechnicalProfile node but it let me through.

    <InputClaim ClaimTypeReferenceId="extension_my_claim" Required="true"/>