Index: variadic_slot.hpp
===================================================================
--- variadic_slot.hpp	(revision 86387)
+++ variadic_slot.hpp	(working copy)
@@ -14,7 +14,7 @@
 #include <boost/signals2/detail/variadic_arg_type.hpp>
 
 #define BOOST_SIGNALS2_SLOT_N_BINDING_CONSTRUCTORS \
-  template<typename ... BindArgs> slot(const BindArgs & ... args) \
+  template<typename ... BindArgs> explicit slot(const BindArgs & ... args) \
   { \
     init_slot_function(boost::bind(args...)); \
   }