diff --git a/Tests/AssemblerLib/TestSerialLinearSolver.cpp b/Tests/AssemblerLib/TestSerialLinearSolver.cpp
index 5318e9cc03996932ffa06fd809283d6b5d02f5ed..ef64f0a9ad5b945dc8c916825eb839eb13702249 100644
--- a/Tests/AssemblerLib/TestSerialLinearSolver.cpp
+++ b/Tests/AssemblerLib/TestSerialLinearSolver.cpp
@@ -19,7 +19,6 @@
 #include "AssemblerLib/VectorMatrixAssembler.h"
 #include "AssemblerLib/LocalAssemblerBuilder.h"
 
-
 #include "MathLib/LinAlg/ApplyKnownSolution.h"
 #include "MathLib/LinAlg/Solvers/GaussAlgorithm.h"
 #include "MathLib/LinAlg/FinalizeMatrixAssembly.h"
@@ -137,8 +136,9 @@ TEST(AssemblerLibSerialLinearSolver, Steady2DdiffusionQuadElem)
         t_root.put_child("eigen", t_solver);
     }
     t_root.put("lis", "-i cg -p none -tol 1e-16 -maxiter 1000");
+    BaseLib::ConfigTreeNew conf(t_root);
 
-    GlobalSetup::LinearSolver ls(*A, "solver_name", &t_root);
+    GlobalSetup::LinearSolver ls(*A, "solver_name", &conf);
     ls.solve(*rhs, *x);
 
     // copy solution to double vector
diff --git a/Tests/MathLib/TestLinearSolver.cpp b/Tests/MathLib/TestLinearSolver.cpp
index 55e68d9b82d84f4979b2907432c5c2cc07cca5a9..7f3f9f6fc9047c0d22cd3500c5b6a77e06bf147e 100644
--- a/Tests/MathLib/TestLinearSolver.cpp
+++ b/Tests/MathLib/TestLinearSolver.cpp
@@ -99,7 +99,7 @@ template<typename IntType> struct Example1
 };
 
 template <class T_MATRIX, class T_VECTOR, class T_LINEAR_SOVLER, typename IntType>
-void checkLinearSolverInterface(T_MATRIX &A, BaseLib::ConfigTree& ls_option)
+void checkLinearSolverInterface(T_MATRIX &A, BaseLib::ConfigTreeNew const& ls_option)
 {
     Example1<IntType> ex1;
 
@@ -136,7 +136,7 @@ void checkLinearSolverInterface(T_MATRIX &A, BaseLib::ConfigTree& ls_option)
 template <class T_MATRIX, class T_VECTOR, class T_LINEAR_SOVLER>
 void checkLinearSolverInterface(T_MATRIX& A, T_VECTOR& b,
                                 const std::string& prefix_name,
-                                BaseLib::ConfigTree& ls_option)
+                                BaseLib::ConfigTreeNew const& ls_option)
 {
     int mrank;
     MPI_Comm_rank(PETSC_COMM_WORLD, &mrank);
@@ -206,6 +206,7 @@ TEST(MathLib, CheckInterface_GaussAlgorithm)
     boost::property_tree::ptree t_root;
     boost::property_tree::ptree t_solver;
     t_root.put_child("ogs", t_solver);
+    BaseLib::ConfigTreeNew conf(t_root);
 
     using Example = Example1<std::size_t>;
 
@@ -213,7 +214,7 @@ TEST(MathLib, CheckInterface_GaussAlgorithm)
     MathLib::GlobalDenseMatrix<double> A(Example::dim_eqs, Example::dim_eqs);
     checkLinearSolverInterface<MathLib::GlobalDenseMatrix<double>,
                                MathLib::DenseVector<double>, LinearSolverType, std::size_t>(
-        A, t_root);
+        A, conf);
 }
 
 #ifdef OGS_USE_EIGEN
@@ -227,12 +228,13 @@ TEST(Math, CheckInterface_Eigen)
     t_solver.put("error_tolerance", 1e-15);
     t_solver.put("max_iteration_step", 1000);
     t_root.put_child("eigen", t_solver);
+    BaseLib::ConfigTreeNew conf(t_root);
 
     using IntType = MathLib::EigenMatrix::IndexType;
 
     MathLib::EigenMatrix A(Example1<IntType>::dim_eqs);
     checkLinearSolverInterface<MathLib::EigenMatrix, MathLib::EigenVector,
-                               MathLib::EigenLinearSolver, IntType>(A, t_root);
+                               MathLib::EigenLinearSolver, IntType>(A, conf);
 }
 #endif
 
@@ -243,12 +245,13 @@ TEST(Math, CheckInterface_EigenLis)
     boost::property_tree::ptree t_root;
     boost::property_tree::ptree t_solver;
     t_root.put("lis", "-i cg -p none -tol 1e-15 -maxiter 1000");
+    BaseLib::ConfigTreeNew conf(t_root);
 
     using IntType = MathLib::LisMatrix::IndexType;
 
     MathLib::EigenMatrix A(Example1<IntType>::dim_eqs);
     checkLinearSolverInterface<MathLib::EigenMatrix, MathLib::EigenVector,
-                               MathLib::EigenLisLinearSolver, IntType>(A, t_root);
+                               MathLib::EigenLisLinearSolver, IntType>(A, conf);
 }
 #endif
 
@@ -259,12 +262,13 @@ TEST(Math, CheckInterface_Lis)
     boost::property_tree::ptree t_root;
     boost::property_tree::ptree t_solver;
     t_root.put("lis", "-i cg -p none -tol 1e-15 -maxiter 1000");
+    BaseLib::ConfigTreeNew conf(t_root);
 
     using IntType = MathLib::LisMatrix::IndexType;
 
     MathLib::LisMatrix A(Example1<IntType>::dim_eqs);
     checkLinearSolverInterface<MathLib::LisMatrix, MathLib::LisVector,
-                               MathLib::LisLinearSolver, IntType>(A, t_root);
+                               MathLib::LisLinearSolver, IntType>(A, conf);
 }
 #endif
 
@@ -292,7 +296,7 @@ TEST(MPITest_Math, CheckInterface_PETSc_Linear_Solver_basic)
     checkLinearSolverInterface<MathLib::PETScMatrix,
                                MathLib::PETScVector,
                                MathLib::PETScLinearSolver>(
-        A, b, "ptest1_", t_root);
+        A, b, "ptest1_", BaseLib::ConfigTreeNew(t_root));
 }
 
 TEST(MPITest_Math, CheckInterface_PETSc_Linear_Solver_chebyshev_sor)
@@ -318,7 +322,7 @@ TEST(MPITest_Math, CheckInterface_PETSc_Linear_Solver_chebyshev_sor)
     checkLinearSolverInterface<MathLib::PETScMatrix,
                                MathLib::PETScVector,
                                MathLib::PETScLinearSolver>(
-        A, b, "ptest2_", t_root);
+        A, b, "ptest2_", BaseLib::ConfigTreeNew(t_root));
 }
 
 TEST(MPITest_Math, CheckInterface_PETSc_Linear_Solver_gmres_amg)
@@ -346,7 +350,7 @@ TEST(MPITest_Math, CheckInterface_PETSc_Linear_Solver_gmres_amg)
     checkLinearSolverInterface<MathLib::PETScMatrix,
                                MathLib::PETScVector,
                                MathLib::PETScLinearSolver>(
-        A, b, "ptest3_", t_root);
+        A, b, "ptest3_", BaseLib::ConfigTreeNew(t_root));
 }
 
 #endif