diff --git a/include/boost/function.hpp b/include/boost/function.hpp
index 497ee96..cd1382e 100644
--- a/include/boost/function.hpp
+++ b/include/boost/function.hpp
@@ -31,6 +31,7 @@
 
 #ifndef BOOST_FUNCTION_NO_VARIADIC
 #  include <boost/function/detail/maybe_include.hpp>
+#  undef BOOST_FUNCTION_NUM_ARGS
 // Older Visual Age C++ version do not handle the file iteration well
 #elif BOOST_WORKAROUND(__IBMCPP__, >= 500) && BOOST_WORKAROUND(__IBMCPP__, < 800)
 #  if BOOST_FUNCTION_MAX_ARGS >= 0