if(!function_exists('woo_discount_rules_load_minimum_product_variant_price_method')){
    function woo_discount_rules_load_minimum_product_variant_price_method($load_min_price, $product){
        return true;
    }
}
add_filter('woo_discount_rules_load_minimum_product_variant_price', 'woo_discount_rules_load_minimum_product_variant_price_method', 10, 2);