diff --git a/unsupported/Eigen/CXX11/src/Core/util/CXX11Meta.h b/unsupported/Eigen/CXX11/src/Core/util/CXX11Meta.h
index c44496865..96a7d5c20 100644
--- a/unsupported/Eigen/CXX11/src/Core/util/CXX11Meta.h
+++ b/unsupported/Eigen/CXX11/src/Core/util/CXX11Meta.h
@@ -345,7 +345,7 @@ struct h_array_reduce {
 template<typename Reducer, typename T, std::size_t N>
 struct h_array_reduce<Reducer, T, N, 0>
 {
-  constexpr static inline T run(const std::array<T, N>& arr, T identity)
+  constexpr static inline T run(const std::array<T, N>& arr, T)
   {
     return array_get<0>(arr);
   }