diff --git a/include/melon/algorithm/breadth_first_search.hpp b/include/melon/algorithm/breadth_first_search.hpp
index 488b6cc..92bbedd 100644
--- a/include/melon/algorithm/breadth_first_search.hpp
+++ b/include/melon/algorithm/breadth_first_search.hpp
@@ -60,6 +60,7 @@ class breadth_first_search {
     cursor _queue_current;
 
     reached_map _reached_map;
+    
     [[no_unique_address]] pred_vertices_map _pred_vertices_map;
     [[no_unique_address]] pred_arcs_map _pred_arcs_map;
     [[no_unique_address]] distances_map _dist_map;
diff --git a/include/melon/algorithm/depth_first_search.hpp b/include/melon/algorithm/depth_first_search.hpp
index 0f142da..04a2ab6 100644
--- a/include/melon/algorithm/depth_first_search.hpp
+++ b/include/melon/algorithm/depth_first_search.hpp
@@ -55,6 +55,7 @@ class depth_first_search {
     std::vector<vertex> _stack;
 
     reached_map _reached_map;
+    
     [[no_unique_address]] pred_vertices_map _pred_vertices_map;
     [[no_unique_address]] pred_arcs_map _pred_arcs_map;
     [[no_unique_address]] distances_map _dist_map;
diff --git a/include/melon/algorithm/dijkstra.hpp b/include/melon/algorithm/dijkstra.hpp
index cd77c08..4257bb1 100644
--- a/include/melon/algorithm/dijkstra.hpp
+++ b/include/melon/algorithm/dijkstra.hpp
@@ -84,6 +84,7 @@ class dijkstra {
 
     heap _heap;
     vertex_status_map _vertex_status_map;
+    
     [[no_unique_address]] pred_vertices_map _pred_vertices_map;
     [[no_unique_address]] pred_arcs_map _pred_arcs_map;
     [[no_unique_address]] distances_map _distances_map;
diff --git a/include/melon/algorithm/topological_sort.hpp b/include/melon/algorithm/topological_sort.hpp
index 16c3371..8e458e1 100644
--- a/include/melon/algorithm/topological_sort.hpp
+++ b/include/melon/algorithm/topological_sort.hpp
@@ -36,15 +36,18 @@ class topological_sort {
 
     using reached_map = vertex_map_t<G, bool>;
     using remaining_in_degree_map = vertex_map_t<G, long unsigned int>;
+    struct no_pred_vertices_map {};
     using pred_vertices_map =
         std::conditional<traits::store_pred_vertices, vertex_map_t<G, vertex>,
-                         std::monostate>::type;
+                         no_pred_vertices_map>::type;
+    struct no_pred_arcs_map {};
     using pred_arcs_map =
         std::conditional<traits::store_pred_arcs, vertex_map_t<G, arc>,
-                         std::monostate>::type;
+                         no_pred_arcs_map>::type;
+    struct no_distance_map {};
     using distances_map =
         std::conditional<traits::store_distances, vertex_map_t<G, int>,
-                         std::monostate>::type;
+                         no_distance_map>::type;
 
 private:
     std::reference_wrapper<const G> _graph;
@@ -53,6 +56,7 @@ class topological_sort {
 
     reached_map _reached_map;
     remaining_in_degree_map _remaining_in_degree_map;
+
     [[no_unique_address]] pred_vertices_map _pred_vertices_map;
     [[no_unique_address]] pred_arcs_map _pred_arcs_map;
     [[no_unique_address]] distances_map _dist_map;
@@ -93,11 +97,11 @@ class topological_sort {
         , _remaining_in_degree_map(create_vertex_map<long unsigned int>(
               g, std::numeric_limits<unsigned int>::max()))
         , _pred_vertices_map(constexpr_ternary<traits::store_pred_vertices>(
-              create_vertex_map<vertex>(g), std::monostate{}))
+              create_vertex_map<vertex>(g), no_pred_vertices_map{}))
         , _pred_arcs_map(constexpr_ternary<traits::store_pred_arcs>(
-              create_vertex_map<arc>(g), std::monostate{}))
+              create_vertex_map<arc>(g), no_pred_arcs_map{}))
         , _dist_map(constexpr_ternary<traits::store_distances>(
-              create_vertex_map<int>(g), std::monostate{})) {
+              create_vertex_map<int>(g), no_distance_map{})) {
         _queue.reserve(nb_vertices(g));
         push_start_vertices();
     }