diff --git a/src/wp-includes/compat.php b/src/wp-includes/compat.php
index 83a8c64652..ab4045250a 100644
--- a/src/wp-includes/compat.php
+++ b/src/wp-includes/compat.php
@@ -122,4 +122,10 @@ function hash_equals( $a, $b ) {
 
 	return $result === 0;
 }
-endif;
\ No newline at end of file
+endif;
+
+// JSON_PRETTY_PRINT was introduced in PHP 5.4
+// Defined here to prevent a notice when using it with wp_json_encode()
+if ( ! defined( 'JSON_PRETTY_PRINT' ) ) {
+	define( 'JSON_PRETTY_PRINT', 128 );
+}