diff --git a/src/wp-includes/post-thumbnail-template.php b/src/wp-includes/post-thumbnail-template.php
index 4722565..9ca2a0c 100644
--- a/src/wp-includes/post-thumbnail-template.php
+++ b/src/wp-includes/post-thumbnail-template.php
@@ -122,11 +122,13 @@ function get_the_post_thumbnail( $post = null, $size = 'post-thumbnail', $attr =
 	 * Filters the post thumbnail size.
 	 *
 	 * @since 2.9.0
+	 * @since 4.9.0 Added the `$post` parameter
 	 *
 	 * @param string|array $size The post thumbnail size. Image size or array of width and height
 	 *                           values (in that order). Default 'post-thumbnail'.
+	 * @param WP_Post      $post The post object
 	 */
-	$size = apply_filters( 'post_thumbnail_size', $size );
+	$size = apply_filters( 'post_thumbnail_size', $size, $post );
 
 	if ( $post_thumbnail_id ) {