diff --git a/externs/olx.js b/externs/olx.js
index 9f69655d9e..78fb0a9f2d 100644
--- a/externs/olx.js
+++ b/externs/olx.js
@@ -7226,7 +7226,8 @@ olx.source.CartoDBOptions.prototype.account;
  *     url: !string,
  *     tierSizeCalculation: (string|undefined),
  *     size: ol.Size,
- *     transition: (number|undefined)}}
+ *     transition: (number|undefined),
+ *     tileSize: (number|undefined)}}
  */
 olx.source.ZoomifyOptions;