diff --git a/src/wp-includes/post-thumbnail-template.php b/src/wp-includes/post-thumbnail-template.php
index 91201e7994..d9b0bdd2eb 100644
--- a/src/wp-includes/post-thumbnail-template.php
+++ b/src/wp-includes/post-thumbnail-template.php
@@ -3,7 +3,7 @@
  * WordPress Post Thumbnail Template Functions.
  *
  * Support for post thumbnails
- * Themes function.php must call add_theme_support( 'post-thumbnails' ) to use these.
+ * Themes functions.php must call add_theme_support( 'post-thumbnails' ) to use these.
  *
  * @package WordPress
  * @subpackage Template