diff --git a/include/boost/unordered/concurrent_flat_map.hpp b/include/boost/unordered/concurrent_flat_map.hpp
index 2a70ea67..d3a0c565 100644
--- a/include/boost/unordered/concurrent_flat_map.hpp
+++ b/include/boost/unordered/concurrent_flat_map.hpp
@@ -795,7 +795,7 @@ namespace boost {
       return c.erase_if(pred);
     }
 
-#ifdef BOOST_UNORDERED_TEMPLATE_DEDUCTION_GUIDES
+#if BOOST_UNORDERED_TEMPLATE_DEDUCTION_GUIDES
 
     template <class InputIterator,
       class Hash =