Index: boost/thread/locks.hpp
===================================================================
--- boost/thread/locks.hpp	(revision 50927)
+++ boost/thread/locks.hpp	(working copy)
@@ -36,8 +36,10 @@ namespace boost
                 true_type dummy[2];
             };
             
+            template<size_t> struct sfinae_type { };
+
             template<typename U>
-            static true_type has_member(U*,void (U::*dummy)()=&U::lock);
+            static true_type has_member(U*,void (U::*dummy)()=&U::lock,sfinae_type<sizeof(&U::unlock)>* = NULL);
             static false_type has_member(void*);
             
             BOOST_STATIC_CONSTANT(bool, value=sizeof(has_member_lock<T>::has_member((T*)NULL))==sizeof(true_type));
@@ -52,8 +54,10 @@ namespace boost
                 true_type dummy[2];
             };
             
+            template<size_t> struct sfinae_type { };
+
             template<typename U>
-            static true_type has_member(U*,void (U::*dummy)()=&U::unlock);
+            static true_type has_member(U*,void (U::*dummy)()=&U::unlock,sfinae_type<sizeof(&U::unlock)>* = NULL);
             static false_type has_member(void*);
             
             BOOST_STATIC_CONSTANT(bool, value=sizeof(has_member_unlock<T>::has_member((T*)NULL))==sizeof(true_type));
@@ -68,8 +72,10 @@ namespace boost
                 true_type dummy[2];
             };
             
+            template<size_t> struct sfinae_type { };
+
             template<typename U>
-            static true_type has_member(U*,bool (U::*dummy)()=&U::try_lock);
+            static true_type has_member(U*,sfinae_type<sizeof(&U::try_lock)>* = NULL,sfinae_type<sizeof(&U::try_lock)>* = NULL);
             static false_type has_member(void*);
             
             BOOST_STATIC_CONSTANT(bool, value=sizeof(has_member_try_lock<T>::has_member((T*)NULL))==sizeof(true_type));