diff --git a/src/ol/source/vector.js b/src/ol/source/vector.js
index 7706fa56fd..ed9c6edde1 100644
--- a/src/ol/source/vector.js
+++ b/src/ol/source/vector.js
@@ -614,7 +614,7 @@ ol.source.Vector.prototype.getClosestFeatureToCoordinate = function(coordinate,
  * `useSpatialIndex` set to `false`.
  * @param {ol.Extent=} opt_extent Destination extent. If provided, no new extent
  *     will be created. Instead, that extent's coordinates will be overwritten.
- * @return {!ol.Extent} Extent.
+ * @return {ol.Extent} Extent.
  * @api
  */
 ol.source.Vector.prototype.getExtent = function(opt_extent) {
diff --git a/src/ol/structs/rbush.js b/src/ol/structs/rbush.js
index f802507dad..d279bd40c1 100644
--- a/src/ol/structs/rbush.js
+++ b/src/ol/structs/rbush.js
@@ -208,7 +208,7 @@ ol.structs.RBush.prototype.clear = function() {
 
 /**
  * @param {ol.Extent=} opt_extent Extent.
- * @return {!ol.Extent} Extent.
+ * @return {ol.Extent} Extent.
  */
 ol.structs.RBush.prototype.getExtent = function(opt_extent) {
   // FIXME add getExtent() to rbush