diff --git a/src/ol/extent/corner.js b/src/ol/extent/corner.js
new file mode 100644
index 0000000000..6c808c47a6
--- /dev/null
+++ b/src/ol/extent/corner.js
@@ -0,0 +1,12 @@
+goog.provide('ol.extent.Corner');
+
+/**
+ * Extent corner.
+ * @enum {string}
+ */
+ol.extent.Corner = {
+  BOTTOM_LEFT: 'bottom-left',
+  BOTTOM_RIGHT: 'bottom-right',
+  TOP_LEFT: 'top-left',
+  TOP_RIGHT: 'top-right'
+};
diff --git a/src/ol/extent.js b/src/ol/extent/index.js
similarity index 99%
rename from src/ol/extent.js
rename to src/ol/extent/index.js
index 2f118d5001..451f27d8d2 100644
--- a/src/ol/extent.js
+++ b/src/ol/extent/index.js
@@ -1,21 +1,9 @@
 goog.provide('ol.extent');
-goog.provide('ol.extent.Corner');
 goog.provide('ol.extent.Relationship');
 
 goog.require('ol');
 goog.require('ol.asserts');
-
-
-/**
- * Extent corner.
- * @enum {string}
- */
-ol.extent.Corner = {
-  BOTTOM_LEFT: 'bottom-left',
-  BOTTOM_RIGHT: 'bottom-right',
-  TOP_LEFT: 'top-left',
-  TOP_RIGHT: 'top-right'
-};
+goog.require('ol.extent.Corner');
 
 
 /**