diff --git a/include/boost/smart_ptr/detail/spinlock.hpp b/include/boost/smart_ptr/detail/spinlock.hpp
index 1640a38..88d7ad6 100644
--- a/include/boost/smart_ptr/detail/spinlock.hpp
+++ b/include/boost/smart_ptr/detail/spinlock.hpp
@@ -31,7 +31,10 @@
 #include <boost/config.hpp>
 #include <boost/smart_ptr/detail/sp_has_sync.hpp>
 
-#if defined(__GNUC__) && defined( __arm__ ) && !defined( __thumb__ )
+#if defined( BOOST_SP_USE_PTHREADS )
+#  include <boost/smart_ptr/detail/spinlock_pt.hpp>
+
+#elif defined(__GNUC__) && defined( __arm__ ) && !defined( __thumb__ )
 #  include <boost/smart_ptr/detail/spinlock_gcc_arm.hpp>
 
 #elif defined( BOOST_SP_HAS_SYNC )