diff --git a/include/boost/shared_ptr.hpp b/include/boost/shared_ptr.hpp
index 98393c2..5e1abd8 100644
--- a/include/boost/shared_ptr.hpp
+++ b/include/boost/shared_ptr.hpp
@@ -383,7 +383,7 @@ public:
 
     // implicit conversion to "bool"
 
-#if ( defined(__SUNPRO_CC) && BOOST_WORKAROUND(__SUNPRO_CC, <= 0x580) ) || defined(__CINT__)
+#if ( defined(__SUNPRO_CC) && BOOST_WORKAROUND(__SUNPRO_CC, < 0x570) ) || defined(__CINT__)
 
     operator bool () const
     {
@@ -405,7 +405,8 @@ public:
 
 #elif \
     ( defined(__MWERKS__) && BOOST_WORKAROUND(__MWERKS__, < 0x3200) ) || \
-    ( defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ < 304) )
+    ( defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ < 304) ) || \
+    ( defined(__SUNPRO_CC) && BOOST_WORKAROUND(__SUNPRO_CC, <= 0x590) )
 
     typedef T * (this_type::*unspecified_bool_type)() const;