diff --git a/include/boost/config/auto_link.hpp b/include/boost/config/auto_link.hpp
index 0c36f7b0..88134d3b 100644
--- a/include/boost/config/auto_link.hpp
+++ b/include/boost/config/auto_link.hpp
@@ -321,9 +321,11 @@ BOOST_LIB_VERSION:    The Boost version, in the form x_y, for Boost version x.y.
 #if defined(BOOST_LIB_NAME)
 #  undef BOOST_LIB_NAME
 #endif
-#if defined(BOOST_LIB_TOOLSET)
-#  undef BOOST_LIB_TOOLSET
-#endif
+// Don't undef this one: it can be set by the user and should be the 
+// same for all libraries:
+//#if defined(BOOST_LIB_TOOLSET)
+//#  undef BOOST_LIB_TOOLSET
+//#endif
 #if defined(BOOST_LIB_THREAD_OPT)
 #  undef BOOST_LIB_THREAD_OPT
 #endif