diff --git a/src/pthread/thread.cpp b/src/pthread/thread.cpp
index 73dd0c31..98737444 100644
--- a/src/pthread/thread.cpp
+++ b/src/pthread/thread.cpp
@@ -395,7 +395,7 @@ namespace boost
 
     bool thread::joinable() const BOOST_NOEXCEPT
     {
-        return (get_thread_info)();
+        return (get_thread_info)()!=0;
     }
 
 
diff --git a/src/win32/thread.cpp b/src/win32/thread.cpp
index 5048c239..3f691e07 100644
--- a/src/win32/thread.cpp
+++ b/src/win32/thread.cpp
@@ -330,7 +330,7 @@ namespace boost
 
     bool thread::joinable() const BOOST_NOEXCEPT
     {
-        return (get_thread_info)();
+        return (get_thread_info)() != 0;
     }
     bool thread::join_noexcept()
     {