Saving lazy-loaded entity with IdClass throws TypeMismatchException

JpaBugTest.java

package org.sapzil;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.ManyToOne;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.transaction.support.TransactionTemplate;

@Repository
interface CompanyRepository extends CrudRepository<JpaBugTest.Company, Integer> {}

@Repository
interface EmployeeRepository extends CrudRepository<JpaBugTest.Employee, JpaBugTest.EmployeeId> {}

@RunWith(SpringRunner.class)
@SpringBootTest
public class JpaBugTest {
    @Autowired
    TransactionTemplate transactionTemplate;
    @Autowired
    CompanyRepository companyRepository;
    @Autowired
    EmployeeRepository employeeRepository;

    @Test
    public void testBug() {
        transactionTemplate.execute(status -> {
            Company company = new Company();
            company.setId(1);
            companyRepository.save(company);

            Employee employee = new Employee();
            employee.setId(1);
            employee.setCompany(company);
            employeeRepository.save(employee);
            return null;
        });

        transactionTemplate.execute(status -> {
            Employee employee = employeeRepository.findById(new EmployeeId(1, 1)).get();
            Company proxiedCompany = employee.getCompany();
            System.out.println(proxiedCompany.getClass()); // class org.sapzil.JpaBugTest$Company_$$_jvst170_3

            Employee employee2 = new Employee();
            employee2.setId(2);
            employee2.setCompany(proxiedCompany);
            employeeRepository.save(employee2);
            return null;
        });
    }

    @SpringBootApplication
    public static class Configuration {}

    @Entity
    public static class Company {
        private Integer id;

        public Company() {}

        @Id
        public Integer getId() {
            return id;
        }

        public void setId(Integer id) {
            this.id = id;
        }
    }

    public static class EmployeeId implements Serializable {
        private Integer company;
        private Integer id;

        public EmployeeId() {}

        public EmployeeId(Integer company, Integer id) {
            this.company = company;
            this.id = id;
        }

        public Integer getCompany() {
            return company;
        }

        public void setCompany(Integer company) {
            this.company = company;
        }

        public Integer getId() {
            return id;
        }

        public void setId(Integer id) {
            this.id = id;
        }
    }

    @Entity
    @IdClass(EmployeeId.class)
    public static class Employee {
        private Integer id;
        private Company company;

        public Employee() {}

        @Id
        public Integer getId() {
            return id;
        }

        public void setId(Integer id) {
            this.id = id;
        }

        @Id
        @ManyToOne(fetch = FetchType.LAZY)
        public Company getCompany() {
            return company;
        }

        public void setCompany(Company company) {
            this.company = company;
        }
    }
}