diff --git a/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h b/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h
index 2d461fe07..fff86bcab 100644
--- a/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h
+++ b/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h
@@ -168,6 +168,7 @@ struct traits<BiCGSTAB<MatrixType_, Preconditioner_> > {
  */
 template <typename MatrixType_, typename Preconditioner_>
 class BiCGSTAB : public IterativeSolverBase<BiCGSTAB<MatrixType_, Preconditioner_> > {
+ protected:
   typedef IterativeSolverBase<BiCGSTAB> Base;
   using Base::m_error;
   using Base::m_info;
diff --git a/Eigen/src/IterativeLinearSolvers/ConjugateGradient.h b/Eigen/src/IterativeLinearSolvers/ConjugateGradient.h
index 5bb0efe8a..9130a3cb7 100644
--- a/Eigen/src/IterativeLinearSolvers/ConjugateGradient.h
+++ b/Eigen/src/IterativeLinearSolvers/ConjugateGradient.h
@@ -150,6 +150,7 @@ struct traits<ConjugateGradient<MatrixType_, UpLo_, Preconditioner_> > {
   */
 template <typename MatrixType_, int UpLo_, typename Preconditioner_>
 class ConjugateGradient : public IterativeSolverBase<ConjugateGradient<MatrixType_, UpLo_, Preconditioner_> > {
+ protected:
   typedef IterativeSolverBase<ConjugateGradient> Base;
   using Base::m_error;
   using Base::m_info;
diff --git a/Eigen/src/IterativeLinearSolvers/LeastSquareConjugateGradient.h b/Eigen/src/IterativeLinearSolvers/LeastSquareConjugateGradient.h
index 182f3190a..b5fa4aac2 100644
--- a/Eigen/src/IterativeLinearSolvers/LeastSquareConjugateGradient.h
+++ b/Eigen/src/IterativeLinearSolvers/LeastSquareConjugateGradient.h
@@ -145,6 +145,7 @@ struct traits<LeastSquaresConjugateGradient<MatrixType_, Preconditioner_> > {
 template <typename MatrixType_, typename Preconditioner_>
 class LeastSquaresConjugateGradient
     : public IterativeSolverBase<LeastSquaresConjugateGradient<MatrixType_, Preconditioner_> > {
+ protected:
   typedef IterativeSolverBase<LeastSquaresConjugateGradient> Base;
   using Base::m_error;
   using Base::m_info;
diff --git a/unsupported/Eigen/src/IterativeSolvers/BiCGSTABL.h b/unsupported/Eigen/src/IterativeSolvers/BiCGSTABL.h
index 0469a5a90..8c49dbc8a 100644
--- a/unsupported/Eigen/src/IterativeSolvers/BiCGSTABL.h
+++ b/unsupported/Eigen/src/IterativeSolvers/BiCGSTABL.h
@@ -280,6 +280,7 @@ struct traits<Eigen::BiCGSTABL<MatrixType_, Preconditioner_>> {
 
 template <typename MatrixType_, typename Preconditioner_>
 class BiCGSTABL : public IterativeSolverBase<BiCGSTABL<MatrixType_, Preconditioner_>> {
+ protected:
   typedef IterativeSolverBase<BiCGSTABL> Base;
   using Base::m_error;
   using Base::m_info;
diff --git a/unsupported/Eigen/src/IterativeSolvers/DGMRES.h b/unsupported/Eigen/src/IterativeSolvers/DGMRES.h
index 2c1050944..b251ff623 100644
--- a/unsupported/Eigen/src/IterativeSolvers/DGMRES.h
+++ b/unsupported/Eigen/src/IterativeSolvers/DGMRES.h
@@ -96,6 +96,7 @@ void sortWithPermutation(VectorType& vec, IndexType& perm, typename IndexType::S
  */
 template <typename MatrixType_, typename Preconditioner_>
 class DGMRES : public IterativeSolverBase<DGMRES<MatrixType_, Preconditioner_> > {
+ protected:
   typedef IterativeSolverBase<DGMRES> Base;
   using Base::m_error;
   using Base::m_info;
diff --git a/unsupported/Eigen/src/IterativeSolvers/GMRES.h b/unsupported/Eigen/src/IterativeSolvers/GMRES.h
index f2c85ffdd..4df83e7f2 100644
--- a/unsupported/Eigen/src/IterativeSolvers/GMRES.h
+++ b/unsupported/Eigen/src/IterativeSolvers/GMRES.h
@@ -253,6 +253,7 @@ struct traits<GMRES<MatrixType_, Preconditioner_> > {
  */
 template <typename MatrixType_, typename Preconditioner_>
 class GMRES : public IterativeSolverBase<GMRES<MatrixType_, Preconditioner_> > {
+ protected:
   typedef IterativeSolverBase<GMRES> Base;
   using Base::m_error;
   using Base::m_info;
diff --git a/unsupported/Eigen/src/IterativeSolvers/IDRSTABL.h b/unsupported/Eigen/src/IterativeSolvers/IDRSTABL.h
index a08a71d04..1ba677382 100644
--- a/unsupported/Eigen/src/IterativeSolvers/IDRSTABL.h
+++ b/unsupported/Eigen/src/IterativeSolvers/IDRSTABL.h
@@ -410,6 +410,7 @@ struct traits<IDRSTABL<MatrixType_, Preconditioner_>> {
 
 template <typename MatrixType_, typename Preconditioner_>
 class IDRSTABL : public IterativeSolverBase<IDRSTABL<MatrixType_, Preconditioner_>> {
+ protected:
   typedef IterativeSolverBase<IDRSTABL> Base;
   using Base::m_error;
   using Base::m_info;
diff --git a/unsupported/Eigen/src/IterativeSolvers/MINRES.h b/unsupported/Eigen/src/IterativeSolvers/MINRES.h
index 9daf5686a..77c6a6c7e 100644
--- a/unsupported/Eigen/src/IterativeSolvers/MINRES.h
+++ b/unsupported/Eigen/src/IterativeSolvers/MINRES.h
@@ -186,6 +186,7 @@ struct traits<MINRES<MatrixType_, UpLo_, Preconditioner_> > {
  */
 template <typename MatrixType_, int UpLo_, typename Preconditioner_>
 class MINRES : public IterativeSolverBase<MINRES<MatrixType_, UpLo_, Preconditioner_> > {
+ protected:
   typedef IterativeSolverBase<MINRES> Base;
   using Base::m_error;
   using Base::m_info;