diff --git a/sound/output.hpp b/sound/output.hpp
index a9012b958..9bbdebb2c 100644
--- a/sound/output.hpp
+++ b/sound/output.hpp
@@ -26,6 +26,7 @@ namespace Sound {
 */
 class Sound;
 typedef boost::shared_ptr<Sound> SoundPtr;
+typedef boost::weak_ptr  <Sound> WSoundPtr;
 
 class Sound
 {
diff --git a/tools/shared_ptr.hpp b/tools/shared_ptr.hpp
index da0b399bd..3d073fc24 100644
--- a/tools/shared_ptr.hpp
+++ b/tools/shared_ptr.hpp
@@ -1,3 +1,3 @@
 // This file should include whatever it needs to define the boost/tr1
-// shared_ptr<> template.
+// shared_ptr<> and weak_ptr<> templates.
 #include <boost/smart_ptr.hpp>