Index: src/wp-includes/deprecated.php
===================================================================
--- src/wp-includes/deprecated.php	(revision 37090)
+++ src/wp-includes/deprecated.php	(working copy)
@@ -3747,6 +3747,7 @@
  * @return string The base URL.
  */
 function _wp_upload_dir_baseurl() {
+	_deprecated_function( __FUNCTION__, '4.5' );
 	$upload_dir = wp_get_upload_dir();
 	return $upload_dir['baseurl'];
 }