diff --git a/core/modules/image/image.admin.inc b/core/modules/image/image.admin.inc
index 9675e98..3ac7bef 100644
--- a/core/modules/image/image.admin.inc
+++ b/core/modules/image/image.admin.inc
@@ -154,7 +154,7 @@ function theme_image_style_preview($variables) {
     '#attributes' => $preview_image,
   );
   $output .= '<div class="preview-image-wrapper">';
-  $output .= check_plain($style->label()) . ' (' . l(t('view actual size'), file_create_url($preview_file) . '?' . time()) . ')';
+  $output .= \Drupal\Component\Utility\String::checkPlain($style->label()) . ' (' . l(t('view actual size'), file_create_url($preview_file) . '?' . time()) . ')';
   $output .= '<div class="preview-image modified-image" style="' . $preview_image['style'] . '">';
   $output .= '<a href="' . file_create_url($preview_file) . '?' . time() . '">' . drupal_render($image) . '</a>';
   $output .= '<div class="height" style="height: ' . $preview_height . 'px"><span>' . $preview_image['height'] . 'px</span></div>';
@@ -213,7 +213,7 @@ function theme_image_resize_summary($variables) {
   $data = $variables['data'];
 
   if ($data['width'] && $data['height']) {
-    return check_plain($data['width']) . 'x' . check_plain($data['height']);
+    return \Drupal\Component\Utility\String::checkPlain($data['width']) . 'x' . \Drupal\Component\Utility\String::checkPlain($data['height']);
   }
   else {
     return ($data['width']) ? t('width @width', array('@width' => $data['width'])) : t('height @height', array('@height' => $data['height']));