diff --git wp-includes/functions.php wp-includes/functions.php
index 5e0841c..6349ab8 100644
--- wp-includes/functions.php
+++ wp-includes/functions.php
@@ -1437,7 +1437,7 @@ function get_temp_dir() {
 /**
  * Determine if a directory is writable.
  *
- * This function is used to work around certain ACL issues 
+ * This function is used to work around certain ACL issues
  * in PHP primarily affecting Windows Servers.
  *
  * @see win_is_writable()
@@ -1457,7 +1457,7 @@ function wp_is_writable( $path ) {
 /**
  * Workaround for Windows bug in is_writable() function
  *
- * PHP has issues with Windows ACL's for determine if a 
+ * PHP has issues with Windows ACL's for determine if a
  * directory is writable or not, this works around them by
  * checking the ability to open files rather than relying
  * upon PHP to interprate the OS ACL.
@@ -2850,17 +2850,19 @@ function url_is_accessable_via_ssl($url)
  * @param string $function The function that was called
  * @param string $version The version of WordPress that deprecated the function
  * @param string $replacement Optional. The function that should have been called
+ * @param string $message Optional. A message regarding the change.
  */
-function _deprecated_function( $function, $version, $replacement = null ) {
+function _deprecated_function( $function, $version, $replacement = null, $message = '' ) {
 
-	do_action( 'deprecated_function_run', $function, $replacement, $version );
+	do_action( 'deprecated_function_run', $function, $replacement, $version, $message );
 
 	// Allow plugin to filter the output error trigger
 	if ( WP_DEBUG && apply_filters( 'deprecated_function_trigger_error', true ) ) {
+		$message = empty( $message ) ? '' : ' ' . $message;
 		if ( ! is_null($replacement) )
-			trigger_error( sprintf( __('%1$s is <strong>deprecated</strong> since version %2$s! Use %3$s instead.'), $function, $version, $replacement ) );
+			trigger_error( sprintf( __('%1$s is <strong>deprecated</strong> since version %2$s! Use %3$s instead.'), $function, $version, $replacement ) . $message );
 		else
-			trigger_error( sprintf( __('%1$s is <strong>deprecated</strong> since version %2$s with no alternative available.'), $function, $version ) );
+			trigger_error( sprintf( __('%1$s is <strong>deprecated</strong> since version %2$s with no alternative available.'), $function, $version ) . $message );
 	}
 }