diff --git a/ProcessLib/HT/MonolithicHTFEM.h b/ProcessLib/HT/MonolithicHTFEM.h
index b3948083223f807d4fd832fc3d8a4a6dbfda1c39..9bbdb9ce77806298397a8b52ff5d9bad232e7fa1 100644
--- a/ProcessLib/HT/MonolithicHTFEM.h
+++ b/ProcessLib/HT/MonolithicHTFEM.h
@@ -81,21 +81,21 @@ public:
         auto local_b = MathLib::createZeroedVector<LocalVectorType>(
             local_b_data, local_matrix_size);
 
-        auto const num_nodes = ShapeFunction::NPOINTS;
-
-        auto Ktt = local_K.template block<num_nodes, num_nodes>(0, 0);
-        auto Mtt = local_M.template block<num_nodes, num_nodes>(0, 0);
-        auto Kpp =
-            local_K.template block<num_nodes, num_nodes>(num_nodes, num_nodes);
-        auto Mpp =
-            local_M.template block<num_nodes, num_nodes>(num_nodes, num_nodes);
-        auto Bp = local_b.template block<num_nodes, 1>(num_nodes, 0);
+        auto Ktt = local_K.template block<temperature_size, temperature_size>(
+            temperature_index, temperature_index);
+        auto Mtt = local_M.template block<temperature_size, temperature_size>(
+            temperature_index, temperature_index);
+        auto Kpp = local_K.template block<pressure_size, pressure_size>(
+            pressure_index, pressure_index);
+        auto Mpp = local_M.template block<pressure_size, pressure_size>(
+            pressure_index, pressure_index);
+        auto Bp = local_b.template block<pressure_size, 1>(pressure_index, 0);
 
         ParameterLib::SpatialPosition pos;
         pos.setElementID(this->_element.getID());
 
-        auto p_nodal_values =
-            Eigen::Map<const NodalVectorType>(&local_x[num_nodes], num_nodes);
+        auto p_nodal_values = Eigen::Map<const NodalVectorType>(
+            &local_x[pressure_index], pressure_size);
 
         auto const& process_data = this->_material_properties;
         auto const& medium =