diff --git a/src/TNL/Solvers/ODE/Euler.h b/src/TNL/Solvers/ODE/Euler.h
index 57c4e10b941d33e524364de7dfc2af20ffd55774..ed98677bc0204a7861ef66740ec92fac23a8c720 100644
--- a/src/TNL/Solvers/ODE/Euler.h
+++ b/src/TNL/Solvers/ODE/Euler.h
@@ -13,6 +13,7 @@
 #include <math.h>
 #include <TNL/Config/ConfigDescription.h>
 #include <TNL/Solvers/ODE/ExplicitSolver.h>
+#include <TNL/Solvers/DummyProblem.h>
 #include <TNL/Config/ParameterContainer.h>
 #include <TNL/Timer.h>
 
@@ -20,7 +21,7 @@ namespace TNL {
 namespace Solvers {
 namespace ODE {
 
-template< typename Problem >
+template< typename Problem = DummyProblem<> >
 class Euler : public ExplicitSolver< Problem >
 {
    public:
diff --git a/src/TNL/Solvers/ODE/Merson.h b/src/TNL/Solvers/ODE/Merson.h
index 84cad93f0a6405d2e6daf1fb239e571d12ff58e5..fd15a9a3bd59e46174b8b773accf4d0dffcd66c2 100644
--- a/src/TNL/Solvers/ODE/Merson.h
+++ b/src/TNL/Solvers/ODE/Merson.h
@@ -11,6 +11,7 @@
 #pragma once
 
 #include <math.h>
+#include <TNL/Solvers/DummyProblem.h>
 #include <TNL/Config/ConfigDescription.h>
 #include <TNL/Solvers/ODE/ExplicitSolver.h>
 
@@ -18,7 +19,7 @@ namespace TNL {
 namespace Solvers {
 namespace ODE {   
 
-template< class Problem >
+template< class Problem = DummyProblem<> >
 class Merson : public ExplicitSolver< Problem >
 {
    public: