diff --git a/src/wp-admin/includes/media.php b/src/wp-admin/includes/media.php
index 75811962f9..086682088a 100644
--- a/src/wp-admin/includes/media.php
+++ b/src/wp-admin/includes/media.php
@@ -1050,6 +1050,14 @@ function image_link_input_fields($post, $url_type = '') {
 ";
 }
 
+/**
+ * Output a textarea element for inputting an attachment caption.
+ *
+ * @since 3.4.0
+ *
+ * @param WP_Post $edit_post Attachment WP_Post object.
+ * @return string HTML markup for the textarea element.
+ */
 function wp_caption_input_textarea($edit_post) {
 	// Post data is already escaped.
 	$name = "attachments[{$edit_post->ID}][post_excerpt]";