diff --git a/Installation/changes.html b/Installation/changes.html
index a9950278076..4804c9aefac 100644
--- a/Installation/changes.html
+++ b/Installation/changes.html
@@ -108,7 +108,8 @@ CGAL 3.10 offers the following improvements and new functionality :  </p>
 <h3>AABB tree</h3>
 <ul>
   <li>Document constness of member functions of the AABB_tree class.</li>
-  <li>The class AABB_tree is now guarantee to be read-only thread-safe.</li>
+  <li>The class AABB_tree is now guarantee to be read-only thread-safe. As usual in CGAL, 
+      this small overhead introduced for thread-safety can be deactivated by defining CGAL_HAS_NO_THREADS.</li>
 </ul>
 
 <h2 id="release3.9">Release 3.9 </h2>