diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorArgMax.h b/unsupported/Eigen/CXX11/src/Tensor/TensorArgMax.h
index c783aab97..781a37e34 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorArgMax.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorArgMax.h
@@ -134,7 +134,7 @@ struct traits<TensorTupleReducerOp<ReduceOp, Dims, XprType> > : public traits<Xp
   typedef Index Scalar;
   typedef typename XprType::Nested Nested;
   typedef typename remove_reference<Nested>::type _Nested;
-  static const int NumDimensions = XprTraits::NumDimensions;
+  static const int NumDimensions = XprTraits::NumDimensions - array_size<Dims>::value;
   static const int Layout = XprTraits::Layout;
 };
 
diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorReduction.h b/unsupported/Eigen/CXX11/src/Tensor/TensorReduction.h
index 8028e71c0..2dc8815b8 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorReduction.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorReduction.h
@@ -24,11 +24,14 @@ template<typename Op, typename Dims, typename XprType>
 struct traits<TensorReductionOp<Op, Dims, XprType> >
  : traits<XprType>
 {
-  typedef typename traits<XprType>::Scalar Scalar;
+  typedef traits<XprType> XprTraits;
+  typedef typename XprTraits::Scalar Scalar;
   typedef typename internal::packet_traits<Scalar>::type Packet;
-  typedef typename traits<XprType>::StorageKind StorageKind;
-  typedef typename traits<XprType>::Index Index;
+  typedef typename XprTraits::StorageKind StorageKind;
+  typedef typename XprTraits::Index Index;
   typedef typename XprType::Nested Nested;
+  static const int NumDimensions = XprTraits::NumDimensions - array_size<Dims>::value;
+  static const int Layout = XprTraits::Layout;
 };
 
 template<typename Op, typename Dims, typename XprType>