diff --git a/src/wp-includes/post-thumbnail-template.php b/src/wp-includes/post-thumbnail-template.php
index a024b1c00b..a648a6f82c 100644
--- a/src/wp-includes/post-thumbnail-template.php
+++ b/src/wp-includes/post-thumbnail-template.php
@@ -179,11 +179,11 @@ function get_the_post_thumbnail( $post = null, $size = 'post-thumbnail', $attr =
  * @param int|WP_Post  $post Optional. Post ID or WP_Post object.  Default is global `$post`.
  * @param string|array $size Optional. Registered image size to retrieve the source for or a flat
  *                           array of height and width dimensions. Default 'post-thumbnail'.
- * @return string Post thumbnail URL or empty string.
+ * @return string|false Post thumbnail URL or false if no URL is available.
  */
 function get_the_post_thumbnail_url( $post = null, $size = 'post-thumbnail' ) {
 	$image = wp_get_attachment_image_url( get_post_thumbnail_id( $post ), $size );
-	return isset( $image ) ? $image : '';
+	return isset( $image ) ? $image : false;
 }
 
 /**