diff --git a/include/boost/graph/detail/array_binary_tree.hpp b/include/boost/graph/detail/array_binary_tree.hpp
index 78755556..e59da9e1 100644
--- a/include/boost/graph/detail/array_binary_tree.hpp
+++ b/include/boost/graph/detail/array_binary_tree.hpp
@@ -63,6 +63,9 @@ public:
       inline iterator& operator++() { ++i; return *this; }
       inline iterator operator++(int)
         { iterator t = *this; ++(*this); return t; }
+      inline iterator& operator--() { --i; return *this; }
+      inline iterator operator--(int)
+        { iterator t = *this; --(*this); return t; }
       inline bool operator==(const iterator& x) const { return i == x.i; }
       inline bool operator!=(const iterator& x) const
         { return !(*this == x); }