diff --git a/wp-admin/includes/export.php b/wp-admin/includes/export.php
index 4fe697e7e6..a77cb804f0 100644
--- a/wp-admin/includes/export.php
+++ b/wp-admin/includes/export.php
@@ -239,10 +239,12 @@ function export_wp( $args = array() ) {
 	 *
 	 * @since 2.1.0
 	 *
-	 * @param string $str String to wrap in XML CDATA tag.
+	 * @param string|null $str String to wrap in XML CDATA tag. May be null.
 	 * @return string
 	 */
 	function wxr_cdata( $str ) {
+		$str = (string) $str;
+
 		if ( ! wp_is_valid_utf8( $str ) ) {
 			$str = utf8_encode( $str );
 		}
diff --git a/wp-includes/version.php b/wp-includes/version.php
index af45aca00b..89877fd01c 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '7.0-alpha-61404';
+$wp_version = '7.0-alpha-61405';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.