Index: boost/fiber/detail/config.hpp
--- boost/fiber/detail/config.hpp.orig
+++ boost/fiber/detail/config.hpp
@@ -38,7 +38,7 @@
 # include <boost/config/auto_link.hpp>
 #endif
 
-#if BOOST_OS_LINUX || BOOST_OS_WINDOWS
+#if BOOST_OS_LINUX || BOOST_OS_BSD_OPEN || BOOST_OS_WINDOWS
 # define BOOST_FIBERS_HAS_FUTEX
 #endif
 
