Bean is expected to be of type 'CourseDAO' but was actually of type 'com.sun.proxy.$Proxy49'

In a training Spring MVC + JPA/Hibernate project, I'm getting the error in question, after I've changed my configuration.

Originally the DAO class was like this:

public Course getById(Integer id) throws DAOException {
        Course result = null;
        try {
            EntityManager em = emf.getFactory().createEntityManager();
            result = em.find(Course.class, id);
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
            throw new DAOException("Could not get Course By Id", e);
        }
        return result;
    }

I was told to spawn EntityManager with @PersistenceContext, and avoid creating new EntityManager every now and then. So I replaced the above EntityManager em = ... line with a @Autowired EntityManager em; field, and changed the JpaConfig class, so it looks like:

@Configuration
@ComponentScan(basePackages = "com.example.school")
@PropertySource("classpath:database.properties")
@EnableTransactionManagement
public class JpaConfig {
    private final Environment environment;

    @Autowired
    public JpaConfig(Environment environment) {
        this.environment = environment;
    }

    @Autowired
    DataSource dataSource;
    
    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() throws NamingException {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(dataSource);
        em.setPackagesToScan("com.example.school");
        JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        em.setJpaVendorAdapter(vendorAdapter);
        return em;
    }

    @Bean
    public PlatformTransactionManager transactionManager(EntityManagerFactory emf) {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(emf);
        return transactionManager;
    }

    @Bean
    public PersistenceExceptionTranslationPostProcessor exceptionTranslation() {
        return new PersistenceExceptionTranslationPostProcessor();
    }
}

While previously the configuration file was that simple:

@Configuration
public class EntityManagerConfig {
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("PU");

    @Bean
    EntityManager em() {
        return emf.createEntityManager();
    }
}

Now I get a stacktrace with the following most important problem in it:

org.springframework.beans.factory.UnsatisfiedDependencyException ...

...

Caused by: org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'courseDAO' is expected to be of type 'com.example.school.dao.CourseDAO' but was actually of type 'com.sun.proxy.$Proxy49' at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1317)

What can be wrong about this configuration?