Ошибка FMXLLoader.load()

Пытаюсь запустить приложение JavaFX, ловлю exception in Application start method. Есть подозрение, что проблемы в пути к файлу .fxml.

public class Main extends Application implements Observer {
    private static final String FXML_MAIN = "fxml/main.fxml";
    public static final String BUNDLES_FOLDER = "Locale";
    private Stage primaryStage;
    private MainController mainController;
    private FXMLLoader fxmlLoader;
    private VBox currentRoot;
    @Override
    public void start(Stage primaryStage) throws Exception {
        this.primaryStage = primaryStage;
        createGUI(LocaleManager.RU_LOCALE);
    }
    public static void main(String[] args) {
        launch(args);
    }
    @Override
    public void update(Observable o, Object arg) {
        Lang lang = (Lang) arg;
        VBox newNode = loadFXML(lang.getLocale()); // получить новое дерево компонетов с нужной локалью
        currentRoot.getChildren().setAll(newNode.getChildren()); // заменить старые дочерник компонента на новые - с другой локалью
    }
    // загружает дерево компонентов и возвращает в виде VBox (корневой элемент в FXML)
    private VBox loadFXML(Locale locale) {
        fxmlLoader = new FXMLLoader();
        fxmlLoader.setLocation(getClass().getResource(FXML_MAIN));
        fxmlLoader.setResources(ResourceBundle.getBundle(BUNDLES_FOLDER, locale));
        VBox node = null;
        try {
            node = (VBox) fxmlLoader.load();
            mainController = fxmlLoader.getController();
            mainController.addObserver(this);
            primaryStage.setTitle(fxmlLoader.getResources().getString("address_book"));
        } catch (IOException e) {
            e.printStackTrace();
        }
        return node;
    }
    private void createGUI(Locale locale) {
        currentRoot = loadFXML(locale);
        Scene scene = new Scene(currentRoot, 300, 275);
        primaryStage.setScene(scene);
        primaryStage.setMinHeight(600);
        primaryStage.setMinWidth(400);
        primaryStage.show();
    }
}

А это вывод ошибок:

Exception in Application start method
    java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
        at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
    Caused by: java.lang.RuntimeException: Exception in Application start method
        at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
        at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$154(LauncherImpl.java:182)
        at java.lang.Thread.run(Thread.java:748)
    Caused by: java.lang.IllegalStateException: Location is not set.
        at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2434)
        at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2409)
        at start.Main.loadFXML(Main.java:56)
        at start.Main.createGUI(Main.java:68)
        at start.Main.start(Main.java:33)
        at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863)
        at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
        at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
        at java.security.AccessController.doPrivileged(Native Method)
        at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
        at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
        at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
        at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
        ... 1 more
    Exception running application start.Main

В чём может быть проблема и как пофиксить?