diff --git a/Eigen/src/misc/Kernel.h b/Eigen/src/misc/Kernel.h
index b9e1518..bef5d6f 100644
--- a/Eigen/src/misc/Kernel.h
+++ b/Eigen/src/misc/Kernel.h
@@ -39,9 +39,8 @@
 {
   typedef _DecompositionType DecompositionType;
   typedef ReturnByValue<kernel_retval_base> Base;
-  typedef typename Base::Index Index;
 
-  kernel_retval_base(const DecompositionType& dec)
+  explicit kernel_retval_base(const DecompositionType& dec)
     : m_dec(dec),
       m_rank(dec.rank()),
       m_cols(m_rank==dec.cols() ? 1 : dec.cols() - m_rank)
@@ -68,7 +67,6 @@
   typedef typename DecompositionType::MatrixType MatrixType; \
   typedef typename MatrixType::Scalar Scalar; \
   typedef typename MatrixType::RealScalar RealScalar; \
-  typedef typename MatrixType::Index Index; \
   typedef Eigen::internal::kernel_retval_base<DecompositionType> Base; \
   using Base::dec; \
   using Base::rank; \