diff --git a/vendor/sll/include/sll/matrix_batch_csr.hpp b/vendor/sll/include/sll/matrix_batch_csr.hpp
index 806647a83..c736c7b97 100644
--- a/vendor/sll/include/sll/matrix_batch_csr.hpp
+++ b/vendor/sll/include/sll/matrix_batch_csr.hpp
@@ -189,7 +189,15 @@ class MatrixBatchCsr : public MatrixBatch<ExecSpace>
     void setup_solver() final
     {
         std::shared_ptr const gko_exec = m_batch_matrix_csr->get_executor();
-
+        //Check if the indices array is sorted, and sort it if necessary.
+        //The values array corresponding to the indices is also reordered.
+        for (size_t i = 0; i < batch_size(); i++) {
+            std::unique_ptr<gko::matrix::Csr<double, int>> tmp_matrix
+                    = m_batch_matrix_csr->create_view_for_item(i);
+            if (!tmp_matrix->is_sorted_by_column_index()) {
+                tmp_matrix->sort_by_column_index();
+            }
+        }
         if constexpr (
                 Solver == MatrixBatchCsrSolver::CG || Solver == MatrixBatchCsrSolver::BICGSTAB) {
             // Create the solver factory
@@ -212,7 +220,7 @@ class MatrixBatchCsr : public MatrixBatch<ExecSpace>
                               .on(gko_exec);
 
             // Create the solvers
-            for (int i = 0; i < batch_size(); i++) {
+            for (size_t i = 0; i < batch_size(); i++) {
                 m_solver.emplace_back(solver_factory->generate(
                         m_batch_matrix_csr->create_const_view_for_item(i)));
             }
@@ -247,7 +255,7 @@ class MatrixBatchCsr : public MatrixBatch<ExecSpace>
 
         if constexpr (
                 Solver == MatrixBatchCsrSolver::CG || Solver == MatrixBatchCsrSolver::BICGSTAB) {
-            for (int i = 0; i < batch_size(); i++) {
+            for (size_t i = 0; i < batch_size(); i++) {
                 std::shared_ptr const gko_exec = m_solver[i]->get_executor();
 
                 // Create a logger to obtain the iteration counts and "implicit" residual norms for every system after the solve.