diff --git a/src/ol/extent.js b/src/ol/extent.js
index 74d951c82d..c352b62b6f 100644
--- a/src/ol/extent.js
+++ b/src/ol/extent.js
@@ -2,6 +2,7 @@ goog.provide('ol.extent');
 goog.provide('ol.extent.Corner');
 goog.provide('ol.extent.Relationship');
 
+goog.require('ol');
 goog.require('ol.asserts');