diff --git a/NumLib/TimeStepping/Algorithms/FixedTimeStepping.cpp b/NumLib/TimeStepping/Algorithms/FixedTimeStepping.cpp
index a9be31c2b58d5abbd358910328280608de28a428..72c255d1261ebefdbd92609ccf16734afe2e9c7a 100644
--- a/NumLib/TimeStepping/Algorithms/FixedTimeStepping.cpp
+++ b/NumLib/TimeStepping/Algorithms/FixedTimeStepping.cpp
@@ -17,7 +17,7 @@
 #include <limits>
 #include <cassert>
 
-#include "BaseLib/ConfigTree.h"
+#include "BaseLib/ConfigTreeNew.h"
 #include "logog/include/logog.hpp"
 
 namespace NumLib
@@ -32,31 +32,15 @@ FixedTimeStepping::FixedTimeStepping(double t0, double tn, double dt)
 {}
 
 FixedTimeStepping*
-FixedTimeStepping::newInstance(BaseLib::ConfigTree const& config)
+FixedTimeStepping::newInstance(BaseLib::ConfigTreeNew const& config)
 {
-    assert(config.get<std::string>("type") == "FixedTimeStepping");
-
-    auto const t_initial = config.get_optional<double>("t_initial");
-    auto const t_end     = config.get_optional<double>("t_end");
-    auto const dt        = config.get_optional<double>("dt");
-
-    if (!t_initial)
-    {
-        ERR("could not find required parameter t_initial.");
-        return nullptr;
-    }
-    if (!t_end)
-    {
-        ERR("could not find required parameter t_end.");
-        return nullptr;
-    }
-    if (!dt)
-    {
-        ERR("could not find required parameter dt.");
-        return nullptr;
-    }
-
-    return new FixedTimeStepping(*t_initial, *t_end, *dt);
+    config.checkConfParam("type", "FixedTimeStepping");
+
+    auto const t_initial = config.getConfParam<double>("t_initial");
+    auto const t_end     = config.getConfParam<double>("t_end");
+    auto const dt        = config.getConfParam<double>("dt");
+
+    return new FixedTimeStepping(t_initial, t_end, dt);
 }
 
 const TimeStep FixedTimeStepping::getTimeStep() const
diff --git a/NumLib/TimeStepping/Algorithms/FixedTimeStepping.h b/NumLib/TimeStepping/Algorithms/FixedTimeStepping.h
index c54ec87ce837f910ac8ea2ccdcbd725ae1f33e39..b258bedc295f9c8e8a9ee6ca383f67b878246fbc 100644
--- a/NumLib/TimeStepping/Algorithms/FixedTimeStepping.h
+++ b/NumLib/TimeStepping/Algorithms/FixedTimeStepping.h
@@ -14,7 +14,7 @@
 
 #include <vector>
 
-#include "BaseLib/ConfigTree.h"
+#include "BaseLib/ConfigTreeNew.h"
 #include "ITimeStepAlgorithm.h"
 
 namespace NumLib
@@ -64,7 +64,7 @@ public:
      *
      * Currently this function only covers uniform timestep size.
      */
-    static FixedTimeStepping* newInstance(BaseLib::ConfigTree const& config);
+    static FixedTimeStepping* newInstance(BaseLib::ConfigTreeNew const& config);
 
     virtual ~FixedTimeStepping() {}