diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorMeta.h b/unsupported/Eigen/CXX11/src/Tensor/TensorMeta.h
index 3952e733c..785321666 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorMeta.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorMeta.h
@@ -110,7 +110,7 @@ namespace internal{
   }
 
   /** Make an array (for index/dimensions) out of a custom index */
-  template<typename Index, int NumIndices, typename IndexType>
+  template<typename Index, std::size_t NumIndices, typename IndexType>
   EIGEN_CONSTEXPR EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
   array<Index, NumIndices> customIndices2Array(IndexType& idx) {
     return customIndices2Array(idx, typename gen_numeric_list<Index, NumIndices>::type{});