diff --git a/src/ol/geom/circle.js b/src/ol/geom/circle.js
index cc32031161..e654472d25 100644
--- a/src/ol/geom/circle.js
+++ b/src/ol/geom/circle.js
@@ -94,20 +94,14 @@ ol.geom.Circle.prototype.getCenter = function() {
 
 /**
  * @inheritDoc
- * @api
  */
-ol.geom.Circle.prototype.getExtent = function(opt_extent) {
-  if (this.extentRevision != this.getRevision()) {
-    var flatCoordinates = this.flatCoordinates;
-    var radius = flatCoordinates[this.stride] - flatCoordinates[0];
-    this.extent = ol.extent.createOrUpdate(
-        flatCoordinates[0] - radius, flatCoordinates[1] - radius,
-        flatCoordinates[0] + radius, flatCoordinates[1] + radius,
-        this.extent);
-    this.extentRevision = this.getRevision();
-  }
-  goog.asserts.assert(goog.isDef(this.extent));
-  return ol.extent.returnOrUpdate(this.extent, opt_extent);
+ol.geom.Circle.prototype.computeExtent = function(extent) {
+  var flatCoordinates = this.flatCoordinates;
+  var radius = flatCoordinates[this.stride] - flatCoordinates[0];
+  return ol.extent.createOrUpdate(
+      flatCoordinates[0] - radius, flatCoordinates[1] - radius,
+      flatCoordinates[0] + radius, flatCoordinates[1] + radius,
+      extent);
 };
 
 
diff --git a/src/ol/geom/geometry.js b/src/ol/geom/geometry.js
index f2c9ebd167..c9981c76f7 100644
--- a/src/ol/geom/geometry.js
+++ b/src/ol/geom/geometry.js
@@ -1,9 +1,9 @@
 goog.provide('ol.geom.Geometry');
 goog.provide('ol.geom.GeometryType');
 
-goog.require('goog.asserts');
 goog.require('goog.functions');
 goog.require('ol.Observable');
+goog.require('ol.extent');
 goog.require('ol.proj');
 
 
@@ -60,9 +60,9 @@ ol.geom.Geometry = function() {
 
   /**
    * @protected
-   * @type {ol.Extent|undefined}
+   * @type {ol.Extent}
    */
-  this.extent = undefined;
+  this.extent = ol.extent.createEmpty();
 
   /**
    * @protected
@@ -134,6 +134,14 @@ ol.geom.Geometry.prototype.containsCoordinate = function(coordinate) {
 };
 
 
+/**
+ * @param {ol.Extent} extent Extent.
+ * @protected
+ * @return {ol.Extent} extent Extent.
+ */
+ol.geom.Geometry.prototype.computeExtent = goog.abstractMethod;
+
+
 /**
  * @param {number} x X.
  * @param {number} y Y.
@@ -144,12 +152,17 @@ ol.geom.Geometry.prototype.containsXY = goog.functions.FALSE;
 
 /**
  * Get the extent of the geometry.
- * @function
  * @param {ol.Extent=} opt_extent Extent.
  * @return {ol.Extent} extent Extent.
  * @api stable
  */
-ol.geom.Geometry.prototype.getExtent = goog.abstractMethod;
+ol.geom.Geometry.prototype.getExtent = function(opt_extent) {
+  if (this.extentRevision != this.getRevision()) {
+    this.extent = this.computeExtent(this.extent);
+    this.extentRevision = this.getRevision();
+  }
+  return ol.extent.returnOrUpdate(this.extent, opt_extent);
+};
 
 
 /**
diff --git a/src/ol/geom/geometrycollection.js b/src/ol/geom/geometrycollection.js
index ca5cb08483..6cbe1c2559 100644
--- a/src/ol/geom/geometrycollection.js
+++ b/src/ol/geom/geometrycollection.js
@@ -1,7 +1,6 @@
 goog.provide('ol.geom.GeometryCollection');
 
 goog.require('goog.array');
-goog.require('goog.asserts');
 goog.require('goog.events');
 goog.require('goog.events.EventType');
 goog.require('goog.object');
@@ -130,21 +129,14 @@ ol.geom.GeometryCollection.prototype.containsXY = function(x, y) {
 
 /**
  * @inheritDoc
- * @api stable
  */
-ol.geom.GeometryCollection.prototype.getExtent = function(opt_extent) {
-  if (this.extentRevision != this.getRevision()) {
-    var extent = ol.extent.createOrUpdateEmpty(this.extent);
-    var geometries = this.geometries_;
-    var i, ii;
-    for (i = 0, ii = geometries.length; i < ii; ++i) {
-      ol.extent.extend(extent, geometries[i].getExtent());
-    }
-    this.extent = extent;
-    this.extentRevision = this.getRevision();
+ol.geom.GeometryCollection.prototype.computeExtent = function(extent) {
+  ol.extent.createOrUpdateEmpty(extent);
+  var geometries = this.geometries_;
+  for (var i = 0, ii = geometries.length; i < ii; ++i) {
+    ol.extent.extend(extent, geometries[i].getExtent());
   }
-  goog.asserts.assert(goog.isDef(this.extent));
-  return ol.extent.returnOrUpdate(this.extent, opt_extent);
+  return extent;
 };
 
 
diff --git a/src/ol/geom/point.js b/src/ol/geom/point.js
index 07ba09ace6..60d85d054b 100644
--- a/src/ol/geom/point.js
+++ b/src/ol/geom/point.js
@@ -73,14 +73,8 @@ ol.geom.Point.prototype.getCoordinates = function() {
 /**
  * @inheritDoc
  */
-ol.geom.Point.prototype.getExtent = function(opt_extent) {
-  if (this.extentRevision != this.getRevision()) {
-    this.extent = ol.extent.createOrUpdateFromCoordinate(
-        this.flatCoordinates, this.extent);
-    this.extentRevision = this.getRevision();
-  }
-  goog.asserts.assert(goog.isDef(this.extent));
-  return ol.extent.returnOrUpdate(this.extent, opt_extent);
+ol.geom.Point.prototype.computeExtent = function(extent) {
+  return ol.extent.createOrUpdateFromCoordinate(this.flatCoordinates, extent);
 };
 
 
diff --git a/src/ol/geom/simplegeometry.js b/src/ol/geom/simplegeometry.js
index 7ead9c8269..ccd82ea539 100644
--- a/src/ol/geom/simplegeometry.js
+++ b/src/ol/geom/simplegeometry.js
@@ -90,17 +90,11 @@ ol.geom.SimpleGeometry.prototype.containsXY = goog.functions.FALSE;
 
 /**
  * @inheritDoc
- * @api stable
  */
-ol.geom.SimpleGeometry.prototype.getExtent = function(opt_extent) {
-  if (this.extentRevision != this.getRevision()) {
-    this.extent = ol.extent.createOrUpdateFromFlatCoordinates(
-        this.flatCoordinates, 0, this.flatCoordinates.length, this.stride,
-        this.extent);
-    this.extentRevision = this.getRevision();
-  }
-  goog.asserts.assert(goog.isDef(this.extent));
-  return ol.extent.returnOrUpdate(this.extent, opt_extent);
+ol.geom.SimpleGeometry.prototype.computeExtent = function(extent) {
+  return ol.extent.createOrUpdateFromFlatCoordinates(
+      this.flatCoordinates, 0, this.flatCoordinates.length, this.stride,
+      extent);
 };