diff --git a/stormpy/lib/stormpy/storage/state.py b/stormpy/lib/stormpy/storage/state.py
index 1faa5fc88..1c31f1f1a 100644
--- a/stormpy/lib/stormpy/storage/state.py
+++ b/stormpy/lib/stormpy/storage/state.py
@@ -28,7 +28,7 @@ class State:
         """ Get actions associated with the state
         :return List of actions
         """
-        row_group_indices = self.model.transition_matrix().row_group_indices()
+        row_group_indices = self.model.transition_matrix()._row_group_indices()
         start = row_group_indices[self.id]
         end = row_group_indices[self.id+1]
         return stormpy.action.Action(start, end, 0, self.model)
diff --git a/stormpy/src/storage/matrix.cpp b/stormpy/src/storage/matrix.cpp
index 79f47633d..526801232 100644
--- a/stormpy/src/storage/matrix.cpp
+++ b/stormpy/src/storage/matrix.cpp
@@ -6,6 +6,7 @@ typedef storm::storage::SparseMatrix<double>::index_type entry_index;
 
 void define_sparse_matrix(py::module& m) {
 
+    // MatrixEntry
     py::class_<storm::storage::MatrixEntry<entry_index, double>>(m, "SparseMatrixEntry", "Entry of sparse matrix")
         .def("__str__", [](storm::storage::MatrixEntry<entry_index, double> const& entry) {
                 std::stringstream stream;
@@ -13,8 +14,8 @@ void define_sparse_matrix(py::module& m) {
                 return stream.str();
             })
         //def_property threw "pointer being freed not allocated" after exiting
-        .def("val", &storm::storage::MatrixEntry<entry_index, double>::getValue, "Value")
-        .def("set_val", &storm::storage::MatrixEntry<entry_index, double>::setValue, "Set value")
+        .def("value", &storm::storage::MatrixEntry<entry_index, double>::getValue, "Value")
+        .def("set_value", &storm::storage::MatrixEntry<entry_index, double>::setValue, py::arg("value"), "Set value")
         .def("column", &storm::storage::MatrixEntry<entry_index, double>::getColumn, "Column")
     ;
  
@@ -30,13 +31,13 @@ void define_sparse_matrix(py::module& m) {
         .def("nr_rows", &storm::storage::SparseMatrix<double>::getRowCount, "Number of rows")
         .def("nr_columns", &storm::storage::SparseMatrix<double>::getColumnCount, "Number of columns")
         .def("nr_entries", &storm::storage::SparseMatrix<double>::getEntryCount, "Number of non-zero entries")
-        .def("row_group_indices", &storm::storage::SparseMatrix<double>::getRowGroupIndices, "Number of non-zero entries")
+        .def("_row_group_indices", &storm::storage::SparseMatrix<double>::getRowGroupIndices, "Get starting rows of row groups")
         .def("get_row", [](storm::storage::SparseMatrix<double>& matrix, entry_index row) {
                 return matrix.getRows(row, row+1);
-            }, py::keep_alive<0, 1>() /* keep_alive seems to avoid problem with wrong values */, "Get rows from start to end")
+            }, py::return_value_policy::reference, py::keep_alive<1, 0>(), py::arg("row"), "Get row")
         .def("get_rows", [](storm::storage::SparseMatrix<double>& matrix, entry_index start, entry_index end) {
                 return matrix.getRows(start, end);
-            }, "Get rows from start to end")
+            }, py::return_value_policy::reference, py::keep_alive<1, 0>(), py::arg("row_start"), py::arg("row_end"), "Get rows from start to end")
         .def("print_row", [](storm::storage::SparseMatrix<double> const& matrix, entry_index row) {
                 std::stringstream stream;
                 auto rows = matrix.getRows(row, row+1);
@@ -47,6 +48,7 @@ void define_sparse_matrix(py::module& m) {
             })
     ;
 
+    // Rows
     py::class_<storm::storage::SparseMatrix<double>::rows>(m, "SparseMatrixRows", "Set of rows in a sparse matrix")
         .def("__iter__", [](storm::storage::SparseMatrix<double>::rows& rows) {
                 return py::make_iterator(rows.begin(), rows.end());
diff --git a/stormpy/src/storage/model.cpp b/stormpy/src/storage/model.cpp
index 04b1eed78..7932dc2d1 100644
--- a/stormpy/src/storage/model.cpp
+++ b/stormpy/src/storage/model.cpp
@@ -17,7 +17,8 @@ std::vector<storm::storage::sparse::state_type> getInitialStates(storm::models::
 }
 
 // Thin wrapper for getting transition matrix
-storm::storage::SparseMatrix<double>& getTransitionMatrix(storm::models::sparse::Model<double>& model) {
+template<typename ValueType>
+storm::storage::SparseMatrix<ValueType>& getTransitionMatrix(storm::models::sparse::Model<ValueType>& model) {
     return model.getTransitionMatrix();
 }
 
@@ -48,20 +49,21 @@ void define_model(py::module& m) {
 
     // Models
     py::class_<storm::models::sparse::Model<double>, std::shared_ptr<storm::models::sparse::Model<double>>>(m, "SparseModel", "A probabilistic model where transitions are represented by doubles and saved in a sparse matrix", py::base<storm::models::ModelBase>())
-        .def("labels", [](storm::models::sparse::Model<double> const& model) {
+        .def("labels", [](storm::models::sparse::Model<double>& model) {
                 return model.getStateLabeling().getLabels();
             }, "Get labels")
         .def("labels_state", &storm::models::sparse::Model<double>::getLabelsOfState, "Get labels")
         .def("initial_states", &getInitialStates<double>, "Get initial states")
-        .def("transition_matrix", &getTransitionMatrix, py::return_value_policy::reference, py::keep_alive<1, 0>(), "Get transition matrix")
+        .def("transition_matrix", &getTransitionMatrix<double>, py::return_value_policy::reference, py::keep_alive<1, 0>(), "Get transition matrix")
     ;    
     py::class_<storm::models::sparse::Dtmc<double>, std::shared_ptr<storm::models::sparse::Dtmc<double>>>(m, "SparseDtmc", "DTMC in sparse representation", py::base<storm::models::sparse::Model<double>>())
     ;
     py::class_<storm::models::sparse::Mdp<double>, std::shared_ptr<storm::models::sparse::Mdp<double>>>(m, "SparseMdp", "MDP in sparse representation", py::base<storm::models::sparse::Model<double>>())
     ;
+
     py::class_<storm::models::sparse::Model<storm::RationalFunction>, std::shared_ptr<storm::models::sparse::Model<storm::RationalFunction>>>(m, "SparseParametricModel", "A probabilistic model where transitions are represented by rational functions and saved in a sparse matrix", py::base<storm::models::ModelBase>())
         .def("collect_probability_parameters", &storm::models::sparse::getProbabilityParameters, "Collect parameters")
-        .def("labels", [](storm::models::sparse::Model<storm::RationalFunction> const& model) {
+        .def("labels", [](storm::models::sparse::Model<storm::RationalFunction>& model) {
                 return model.getStateLabeling().getLabels();
             }, "Get labels")
         .def("labels_state", &storm::models::sparse::Model<storm::RationalFunction>::getLabelsOfState, "Get labels")
diff --git a/stormpy/tests/storage/test_matrix.py b/stormpy/tests/storage/test_matrix.py
index 23beb8ece..0f02f3193 100644
--- a/stormpy/tests/storage/test_matrix.py
+++ b/stormpy/tests/storage/test_matrix.py
@@ -9,20 +9,20 @@ class TestMatrix:
         assert matrix.nr_columns() == model.nr_states()
         assert matrix.nr_entries() == 27 #model.nr_transitions()
         for e in matrix:
-            assert e.val() == 0.5 or e.val() == 0 or (e.val() == 1 and e.column() > 6)
+            assert e.value() == 0.5 or e.value() == 0 or (e.value() == 1 and e.column() > 6)
     
     def test_change_sparse_matrix(self):
         model = stormpy.parse_explicit_model("../examples/dtmc/die/die.tra", "../examples/dtmc/die/die.lab")
         matrix = model.transition_matrix()
         for e in matrix:
-            assert e.val() == 0.5 or e.val() == 0 or e.val() == 1
+            assert e.value() == 0.5 or e.value() == 0 or e.value() == 1
         i = 0
         for e in matrix:
-            e.set_val(i)
+            e.set_value(i)
             i += 0.1
         i = 0
         for e in matrix:
-            assert e.val() == i
+            assert e.value() == i
             i += 0.1
     
     def test_change_sparse_matrix_modelchecking(self):
@@ -31,7 +31,7 @@ class TestMatrix:
         matrix = model.transition_matrix()
         # Check matrix
         for e in matrix:
-            assert e.val() == 0.5 or e.val() == 0 or e.val() == 1
+            assert e.value() == 0.5 or e.value() == 0 or e.value() == 1
         # First model checking
         formulas = stormpy.parse_formulas("P=? [ F \"one\" ]")
         result = stormpy.model_checking(model, formulas[0])
@@ -40,14 +40,14 @@ class TestMatrix:
         # Change probabilities
         i = 0
         for e in matrix:
-            if e.val() == 0.5:
+            if e.value() == 0.5:
                 if i % 2 == 0:
-                    e.set_val(0.3)
+                    e.set_value(0.3)
                 else:
-                    e.set_val(0.7)
+                    e.set_value(0.7)
                 i += 1
         for e in matrix:
-            assert e.val() == 0.3 or e.val() == 0.7 or e.val() == 1 or e.val() == 0
+            assert e.value() == 0.3 or e.value() == 0.7 or e.value() == 1 or e.value() == 0
         # Second model checking
         result = stormpy.model_checking(model, formulas[0])
         assert result == 0.06923076923076932
@@ -56,10 +56,10 @@ class TestMatrix:
         for state in stormpy.state.State(0, model):
             for action in state.actions():
                 for transition in action.transitions():
-                    if transition.val() == 0.3:
-                        transition.set_val(0.8)
-                    elif transition.val() == 0.7:
-                        transition.set_val(0.2)
+                    if transition.value() == 0.3:
+                        transition.set_value(0.8)
+                    elif transition.value() == 0.7:
+                        transition.set_value(0.2)
         # Third model checking
         result = stormpy.model_checking(model, formulas[0])
         assert result == 0.3555555555555556 or result == 0.3555555555555557
diff --git a/stormpy/tests/storage/test_model_iterators.py b/stormpy/tests/storage/test_model_iterators.py
index 9b090b9bb..2705aa3e1 100644
--- a/stormpy/tests/storage/test_model_iterators.py
+++ b/stormpy/tests/storage/test_model_iterators.py
@@ -50,7 +50,7 @@ class TestModelIterators:
                     i += 1
                     assert state.id == transition_orig[0]
                     assert transition.column() == transition_orig[1]
-                    assert transition.val() == transition_orig[2]
+                    assert transition.value() == transition_orig[2]
     
     def test_transitions_mdp(self):
         model = stormpy.parse_explicit_model("../examples/mdp/two_dice/two_dice.tra", "../examples/mdp/two_dice/two_dice.lab")
@@ -60,5 +60,5 @@ class TestModelIterators:
             for action in state.actions():
                 i += 1
                 for transition in action.transitions():
-                    assert transition.val() == 0.5 or transition.val() == 1
+                    assert transition.value() == 0.5 or transition.value() == 1
             assert i == 1 or i == 2