Index: wp-includes/wp-db.php
===================================================================
--- wp-includes/wp-db.php	(revision 21274)
+++ wp-includes/wp-db.php	(working copy)
@@ -545,6 +545,14 @@
 	 * @param string   $collate The collation (optional)
 	 */
 	function set_charset($dbh, $charset = null, $collate = null) {
+		if ( version_compare( mysql_get_server_info(), '5.5.3', '>=' ) ) {
+			if ( 'utf8' == $this->charset )
+				$this->charset = 'utf8mb4';
+
+			if ( strpos( $this->charset, 'utf8_' ) === 0 )
+				$this->charset = str_replace( 'utf8_', 'utf8mb4_', $this->charset );
+		}
+
 		if ( !isset($charset) )
 			$charset = $this->charset;
 		if ( !isset($collate) )