diff --git a/externs/olx.js b/externs/olx.js
index 9c2bde6b7c..ac24633afa 100644
--- a/externs/olx.js
+++ b/externs/olx.js
@@ -2818,6 +2818,7 @@ olx.source.TileImageOptions.prototype.tileUrlFunction;
  * @typedef {{attributions: (Array.<ol.Attribution>|undefined),
  *     defaultProjection: ol.proj.ProjectionLike,
  *     extent: (ol.Extent|undefined),
+ *     format: ol.format.Feature,
  *     logo: (string|undefined),
  *     object: (GeoJSONObject|undefined),
  *     projection: ol.proj.ProjectionLike,
@@ -2851,6 +2852,13 @@ olx.source.TileVectorOptions.prototype.defaultProjection;
 olx.source.TileVectorOptions.prototype.extent;
 
 
+/**
+ * Format.
+ * @type {ol.format.Feature}
+ */
+olx.source.TileVectorOptions.prototype.format;
+
+
 /**
  * Logo.
  * @type {string|undefined}