diff --git a/src/ol/geolocation.js b/src/ol/geolocation.js
index a619db1b1f..81bdc95d1b 100644
--- a/src/ol/geolocation.js
+++ b/src/ol/geolocation.js
@@ -49,7 +49,7 @@ ol.Geolocation = function() {
    * @private
    * @type {number|undefined}
    */
-  this.watchId_;
+  this.watchId_ = undefined;
 
   this.setTracking(false);