diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index 0fb2117835..9f229291a7 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -2662,7 +2662,9 @@ function wp_json_encode( $data, $options = 0, $depth = 512 ) {
 	$json = call_user_func_array( 'json_encode', $args );
 
 	// If json_encode() was successful, no need to do more sanity checking.
-	if ( false !== $json ) {
+	// ... unless we're in an old version of PHP, and json_encode() returned
+	// a string containing 'null'. Then we need to do more sanity checking.
+	if ( false !== $json && ( version_compare( PHP_VERSION, '5.5', '>=' ) || false === strpos( $json, 'null' ) ) )  {
 		return $json;
 	}
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index eedce7f17b..d178f218cd 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.1-beta2-30560';
+$wp_version = '4.1-beta2-30561';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.