diff --git a/src/TNL/Solvers/IterativeSolverMonitor.h b/src/TNL/Solvers/IterativeSolverMonitor.h
index 02a224703e813f51d81b27e6b65760c1291a84d6..401e34c23a6183075dff5dd64c039ba066ac4bd5 100644
--- a/src/TNL/Solvers/IterativeSolverMonitor.h
+++ b/src/TNL/Solvers/IterativeSolverMonitor.h
@@ -21,7 +21,8 @@ namespace TNL {
  * \tparam Real is a type of the floating-point arithmetics.
  * \tparam Index is an indexing type.
  */
-template< typename Real, typename Index>
+template< typename Real = double,
+          typename Index = int >
 class IterativeSolverMonitor : public SolverMonitor
 {
    public: