diff --git a/include/boost/detail/atomic_count_gcc.hpp b/include/boost/detail/atomic_count_gcc.hpp
index c3d29a8..b4a46ce 100644
--- a/include/boost/detail/atomic_count_gcc.hpp
+++ b/include/boost/detail/atomic_count_gcc.hpp
@@ -51,7 +51,7 @@ private:
     atomic_count(atomic_count const &);
     atomic_count & operator=(atomic_count const &);
 
-    _Atomic_word value_;
+    mutable _Atomic_word value_;
 };
 
 } // namespace detail