magento2 – Replace thumbnail with small image in Admin Catalog Products

I’d like to display “small image” in place of “thumbnail image” for each product in magento administration Catalog > Products.

I tried editing file /vendor/magento/module-catalog/Ui/Component/Listing/Columns/Thumbnail.php like this:

public function prepareDataSource(array $dataSource)
    {
        if (isset($dataSource('data')('items'))) {
            $fieldName = $this->getData('name');
            foreach ($dataSource('data')('items') as & $item) {
                $product = new MagentoFrameworkDataObject($item);
                $imageHelper = $this->imageHelper->init($product, 'small_image');
                $item($fieldName . '_src') = $imageHelper->getUrl();
                $item($fieldName . '_alt') = $this->getAlt($item) ?: $imageHelper->getLabel();
                $item($fieldName . '_link') = $this->urlBuilder->getUrl(
                    'catalog/product/edit',
                    ('id' => $product->getEntityId(), 'store' => $this->context->getRequestParam('store'))
                );
                $origImageHelper = $this->imageHelper->init($product, 'small_image');
                $item($fieldName . '_orig_src') = $origImageHelper->getUrl();
            }
        }

        return $dataSource;
    }

but it didn’t work. Any ideas?