diff --git a/src/wp-includes/compat.php b/src/wp-includes/compat.php
index b2308e8f22..781e7a728f 100644
--- a/src/wp-includes/compat.php
+++ b/src/wp-includes/compat.php
@@ -315,4 +315,20 @@ if ( ! function_exists( 'json_last_error_msg' ) ) :
 				return 'An unknown error occurred';
 		}
 	}
-endif;
\ No newline at end of file
+endif;
+
+if ( ! interface_exists( 'JsonSerializable' ) ) {
+	define( 'WP_JSON_SERIALIZE_COMPATIBLE', true );
+	/**
+	 * JsonSerializable interface.
+	 *
+	 * Compatibility shim for PHP <5.4
+	 *
+     * @link http://php.net/jsonserializable
+	 *
+	 * @since 4.4.0
+	 */
+	interface JsonSerializable {
+		public function jsonSerialize();
+	}
+}