No custom field variable when duplicating product

Hi,

When duplicating a product which contains a custom field, the variable of that custom field isn’t being duplicated.

I use my own customized code instead of a plugin for my custom field:

Add field:

function wc_extra_product_fields() {
	woocommerce_wp_text_input( array( 'id' => 'my_field', 'label' => __('Field name') ) );
}
add_action( 'woocommerce_product_options_pricing', 'wc_extra_product_fields' );

Save field:

function wc_save_extra_product_fields( $post_id ) {
	update_post_meta( $post_id, 'my_field', esc_attr( $_POST['my_field'] ) );
}
add_action( 'woocommerce_process_product_meta', 'wc_save_extra_product_fields' );

Code above works fine. So only having trouble when duplicating a product.

Any help appreciated.

Guido