diff --git a/STL_Extension/include/CGAL/internal/boost/array_binary_tree.hpp b/STL_Extension/include/CGAL/internal/boost/array_binary_tree.hpp
index dc9e8a6b4e5..e2d5ebd2f66 100644
--- a/STL_Extension/include/CGAL/internal/boost/array_binary_tree.hpp
+++ b/STL_Extension/include/CGAL/internal/boost/array_binary_tree.hpp
@@ -55,7 +55,7 @@ public:
     { // replace with iterator_adaptor implementation -JGS
       typedef std::forward_iterator_tag Category;
       typedef ArrayBinaryTreeNode value_type;
-      typedef size_type difference_type
+      typedef size_type difference_type;
       typedef ArrayBinaryTreeNode* Pointer;
       typedef ArrayBinaryTreeNode& Reference;