diff --git a/externs/olx.js b/externs/olx.js
index 60da9abb15..be9053b422 100644
--- a/externs/olx.js
+++ b/externs/olx.js
@@ -5155,6 +5155,12 @@ olx.source.VectorOptions.prototype.strategy;
  * the given URL. Use a {@link ol.FeatureUrlFunction} to generate the url with
  * other loading strategies.
  * Requires `format` to be set as well.
+ * When default XHR feature loader is provided, the features will
+ * be transformed from the data projection to the view projection 
+ * during parsing. If your remote data source does not advertise its projection 
+ * properly, this transformation will be incorrect. For some formats, the 
+ * default projection (usually EPSG:4326) can be overridden by setting the 
+ * defaultDataProjection constructor option on the format.
  * @type {string|ol.FeatureUrlFunction|undefined}
  * @api
  */