diff --git a/src/ol/structs/rbush.js b/src/ol/structs/rbush.js
index e2342e512b..2af41213e9 100644
--- a/src/ol/structs/rbush.js
+++ b/src/ol/structs/rbush.js
@@ -93,6 +93,31 @@ ol.structs.RBushNode.compareMinY = function(node1, node2) {
 };
 
 
+/**
+ * @param {boolean} isRoot Is root.
+ * @param {number} minEntries Min entries.
+ * @param {number} maxEntries Max entries.
+ */
+ol.structs.RBushNode.prototype.assertValid =
+    function(isRoot, minEntries, maxEntries) {
+  if (this.height === 0) {
+    goog.asserts.assert(goog.isNull(this.children));
+    goog.asserts.assert(!goog.isNull(this.value));
+  } else {
+    goog.asserts.assert(!goog.isNull(this.children));
+    goog.asserts.assert(goog.isNull(this.value));
+    goog.asserts.assert(isRoot || minEntries <= this.children.length);
+    goog.asserts.assert(this.children.length <= maxEntries);
+    var i, ii;
+    for (i = 0, ii = this.children.length; i < ii; ++i) {
+      var child = this.children[i];
+      goog.asserts.assert(ol.extent.containsExtent(this.extent, child.extent));
+      child.assertValid(false, minEntries, maxEntries);
+    }
+  }
+};
+
+
 /**
  * @param {number} start Start.
  * @param {number} stop Stop.
@@ -233,6 +258,14 @@ ol.structs.RBush.prototype.allInExtent = function(extent) {
 };
 
 
+/**
+ * FIXME empty description for jsdoc
+ */
+ol.structs.RBush.prototype.assertValid = function() {
+  this.root_.assertValid(true, this.minEntries_, this.maxEntries_);
+};
+
+
 /**
  * @param {ol.structs.RBushNode.<T>} node Node.
  * @private