diff --git a/include/boost/asio/io_service.hpp b/include/boost/asio/io_service.hpp
index 5e337835..27aabb10 100644
--- a/include/boost/asio/io_service.hpp
+++ b/include/boost/asio/io_service.hpp
@@ -40,6 +40,11 @@
 namespace boost {
 namespace asio {
 
+class io_service;
+template <typename Service> Service& use_service(io_service& ios);
+template <typename Service> void add_service(io_service& ios, Service* svc);
+template <typename Service> bool has_service(io_service& ios);
+
 /// Provides core I/O functionality.
 /**
  * The io_service class provides the core I/O functionality for users of the