         /// Zip code. Example: `"94043"`
         public var zipCode: String?
         
-        /// This is the field type used by the IPAPI service to filter out unnecessary data.
-        public enum CodingKeys: String, CodingKey {
+        /// This enum defines the property names used by the REST API.
+        public enum CodingKeys: String, CodingKey, Codable {
             /// AS number and name.
             case `as` = "as"
             /// City.

            return nil
        }
        
        let body = queries.map { $0.toJSON() }
        guard let jsonBody = try? JSONSerialization.data(withJSONObject: body, options: []) else {
            completion?(nil, Error.invalidRequestData)
            return nil

            self.language = language
        }
    }
    
    // MARK: - Constants -
    
