diff --git a/include/boost/sort/common/spinlock.hpp b/include/boost/sort/common/spinlock.hpp
index 5944e21..5287ccb 100644
--- a/include/boost/sort/common/spinlock.hpp
+++ b/include/boost/sort/common/spinlock.hpp
@@ -70,7 +70,7 @@ class spinlock_t
     //-------------------------------------------------------------------------
     bool try_lock ( ) noexcept
     {
-        return not af.test_and_set (std::memory_order_acquire);
+        return !af.test_and_set (std::memory_order_acquire);
     };
     //
     //-------------------------------------------------------------------------