Actions V1 not populating custom claims in ID Token for OIDC (Zitadel v4.13.1)

function transformRoles(ctx, api) {
    var roles = ctx.v1.user.getProjectRoles();
    var roleNames = [];
    
    if (roles) {
        roleNames = Object.keys(roles);
    }
    
    if (roleNames.length === 0) {
        roleNames.push("jira-users");
    }
    
    api.v1.claims.setClaim('custom_groups', roleNames);
}

// jwtClaimsSet.getClaims() result:
{
  "iss": "https://zitadel.mycompany.com",
  "sub": "***",
  "aud": ["***", "***"],
  "name": "MyName MySurname",
  "email": "myname@mycompany.com",
  ...
  // MISSING: "custom_groups" or "groups" as a flat array
}