diff --git a/wp-includes/class-wp-customize-setting.php b/wp-includes/class-wp-customize-setting.php
index c7cff51fe5..af850098ce 100644
--- a/wp-includes/class-wp-customize-setting.php
+++ b/wp-includes/class-wp-customize-setting.php
@@ -1151,6 +1151,11 @@ class WP_Customize_Nav_Menu_Item_Setting extends WP_Customize_Setting {
 				$this->value[ $key ] = intval( $this->value[ $key ] );
 			}
 		}
+		foreach ( array( 'classes', 'xfn' ) as $key ) {
+			if ( is_array( $this->value[ $key ] ) ) {
+				$this->value[ $key ] = implode( ' ', $this->value[ $key ] );
+			}
+		}
 
 		if ( ! isset( $this->value['_invalid'] ) ) {
 			$this->value['_invalid'] = (
diff --git a/wp-includes/version.php b/wp-includes/version.php
index d141779346..a16658cfa7 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.4-alpha-35307';
+$wp_version = '4.4-alpha-35308';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.