diff --git a/src/ol/collection.exports b/src/ol/collection.exports
index 11b7e20c8f..5e3dae2d8d 100644
--- a/src/ol/collection.exports
+++ b/src/ol/collection.exports
@@ -1,5 +1,6 @@
 @exportSymbol ol.Collection
 @exportProperty ol.Collection.prototype.clear
+@exportProperty ol.Collection.prototype.extend
 @exportProperty ol.Collection.prototype.forEach
 @exportProperty ol.Collection.prototype.getAt
 @exportProperty ol.Collection.prototype.getLength