Index: src/wp-includes/class-wp-editor.php
===================================================================
--- src/wp-includes/class-wp-editor.php	(revision 28084)
+++ src/wp-includes/class-wp-editor.php	(working copy)
@@ -982,6 +982,11 @@
 		$baseurl = self::$baseurl;
 		$mce_locale = self::$mce_locale;
 
+		// Set direction
+		if ( is_rtl() ) {
+			$mce_translation['_dir'] = 'rtl';
+		}
+
 		/**
 		 * Filter translated strings prepared for TinyMCE.
 		 *
Index: src/wp-includes/css/editor.css
===================================================================
--- src/wp-includes/css/editor.css	(revision 28084)
+++ src/wp-includes/css/editor.css	(working copy)
@@ -1851,6 +1851,11 @@
 	font-family: Tahoma, sans-serif;
 }
 
+/* Has to be 'ltr' so it gets swapped with 'rtl' by cssjanus? */
+.mce-rtl .mce-flow-layout > div > div {
+	direction: ltr;
+}
+
 html:lang(he-il) .rtl .wp-switch-editor,
 html:lang(he-il) .rtl .quicktags-toolbar input  {
  	font-family: Arial, sans-serif;
Index: src/wp-includes/functions.php
===================================================================
--- src/wp-includes/functions.php	(revision 28084)
+++ src/wp-includes/functions.php	(working copy)
@@ -2470,7 +2470,7 @@
 	if ( is_rtl() ) {
 		$input['directionality'] = 'rtl';
 		$input['plugins'] .= ',directionality';
-		$input['theme_advanced_buttons1'] .= ',ltr';
+		$input['toolbar1'] .= ',ltr';
 	}
 
 	return $input;