diff --git a/AABB_tree/include/CGAL/AABB_tree.h b/AABB_tree/include/CGAL/AABB_tree.h
index 998064153ea..95269c99a0b 100644
--- a/AABB_tree/include/CGAL/AABB_tree.h
+++ b/AABB_tree/include/CGAL/AABB_tree.h
@@ -28,7 +28,6 @@
 #include <boost/optional.hpp>
 
 #ifdef CGAL_HAS_THREADS
-#warning USING THEADS
 #include <boost/thread/mutex.hpp>
 #endif