diff --git a/unsupported/test/cxx11_tensor_reduction.cpp b/unsupported/test/cxx11_tensor_reduction.cpp
index 0ec316991..6a128901a 100644
--- a/unsupported/test/cxx11_tensor_reduction.cpp
+++ b/unsupported/test/cxx11_tensor_reduction.cpp
@@ -9,6 +9,7 @@
 
 #include "main.h"
 #include <limits>
+#include <numeric>
 #include <Eigen/CXX11/Tensor>
 
 using Eigen::Tensor;