Problem with proxy when using #IdClass in Hibernate - spring

Question

For legacy reasons I have composite keys in my database, I use #IdClass to map them (before I used #Embeddedid but it had it's own bugs). However I have problem whenever I'm trying to save composite key entity that contains proxy as id field.
I made very simple example to isolate this problem (example uses Spring Data, but I think its irrelevant).
p.s. I know that calling .save is not necessary, but it should not cause exception.
#Entity
public class Image {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String fileName;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getFileName() {
return fileName;
}
public void setFileName(String fileName) {
this.fileName = fileName;
}
}
#Entity
public class Product {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
#Entity
#IdClass(ProductImage.ProductImageId.class)
public class ProductImage {
public static class ProductImageId implements Serializable {
private static final long serialVersionUID = 8542391285589067304L;
private Long product;
private Long image;
public ProductImageId() {
}
public Long getProduct() {
return product;
}
public void setProduct(Long product) {
this.product = product;
}
public Long getImage() {
return image;
}
public void setImage(Long image) {
this.image = image;
}
#Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
ProductImageId that = (ProductImageId) o;
return Objects.equals(product, that.product) &&
Objects.equals(image, that.image);
}
#Override
public int hashCode() {
return Objects.hash(product, image);
}
}
#ManyToOne(fetch = FetchType.LAZY)
#Id
private Product product;
#ManyToOne(fetch = FetchType.LAZY)
#Id
private Image image;
private Integer number;
public Product getProduct() {
return product;
}
public void setProduct(Product product) {
this.product = product;
}
public Image getImage() {
return image;
}
public void setImage(Image image) {
this.image = image;
}
public Integer getNumber() {
return number;
}
public void setNumber(Integer number) {
this.number = number;
}
}
List<ProductImage> productImages = productImageRepository.findAll();
productImages.get(0).setNumber(456);
productImageRepository.save(productImages.get(0));
Caused by: java.lang.IllegalArgumentException: Cannot convert value of type 'com.example.springbootnewplayground.Product$HibernateProxy$AJ38NiN6' to required type 'java.lang.Long' for property 'product': PropertyEditor [org.springframework.beans.propertyeditors.CustomNumberEditor] returned inappropriate value of type 'com.example.springbootnewplayground.Product$HibernateProxy$AJ38NiN6'
at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:258) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.AbstractNestablePropertyAccessor.convertIfNecessary(AbstractNestablePropertyAccessor.java:585) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
... 69 common frames omitted