diff --git a/Envelope_2/include/CGAL/Envelope_2/Env_divide_and_conquer_2_impl.h b/Envelope_2/include/CGAL/Envelope_2/Env_divide_and_conquer_2_impl.h
index af0f793f4ed..f813f8ccc9a 100644
--- a/Envelope_2/include/CGAL/Envelope_2/Env_divide_and_conquer_2_impl.h
+++ b/Envelope_2/include/CGAL/Envelope_2/Env_divide_and_conquer_2_impl.h
@@ -609,9 +609,7 @@ _merge_two_intervals(Edge_const_handle e1, bool is_leftmost1,
   // This is the rightmost vertex in the current minimization diagram (out_d).
   // The intersection points/curves that interest us are the ones in
   // [v_leftmost, v].
-  // Without using make_optional we get a "maybe uninitialized" warning with gcc -Wall
-  std::optional<Vertex_const_handle>  v_leftmost =
-    std::make_optional(false, Vertex_const_handle());
+  std::optional<Vertex_const_handle>  v_leftmost;
 
   if (is_leftmost1 == true) {
     if (is_leftmost2 == false)
diff --git a/Mesh_3/include/CGAL/Mesh_3/Protect_edges_sizing_field.h b/Mesh_3/include/CGAL/Mesh_3/Protect_edges_sizing_field.h
index d2f1065785a..81140cdc66e 100644
--- a/Mesh_3/include/CGAL/Mesh_3/Protect_edges_sizing_field.h
+++ b/Mesh_3/include/CGAL/Mesh_3/Protect_edges_sizing_field.h
@@ -1524,7 +1524,7 @@ change_ball_size(const Vertex_handle& v, const FT squared_size, const bool speci
   Bare_point p = cp(c3t3_.triangulation().point(v)); // intentional copy
 
   // Remove v from the set of corners
-  std::optional<Corner_index> corner_index = std::make_optional(false, Corner_index());
+  std::optional<Corner_index> corner_index;
   if ( c3t3_.is_in_complex(v) )
   {
     corner_index = c3t3_.corner_index(v);
diff --git a/Periodic_3_mesh_3/include/CGAL/Periodic_3_mesh_3/Protect_edges_sizing_field.h b/Periodic_3_mesh_3/include/CGAL/Periodic_3_mesh_3/Protect_edges_sizing_field.h
index d46e847a2c0..e35eb180ba6 100644
--- a/Periodic_3_mesh_3/include/CGAL/Periodic_3_mesh_3/Protect_edges_sizing_field.h
+++ b/Periodic_3_mesh_3/include/CGAL/Periodic_3_mesh_3/Protect_edges_sizing_field.h
@@ -2479,7 +2479,7 @@ change_ball_size(Vertex_handle& v, const FT squared_size, const bool special_bal
   const Bare_point p = cp(c3t3_.triangulation().point(v)); // intentional copy
 
   // Remove v from the set of corners
-  std::optional<Corner_index> corner_index = std::make_optional(false, Corner_index());
+  std::optional<Corner_index> corner_index;
   if(c3t3_.is_in_complex(v))
   {
     corner_index = c3t3_.corner_index(v);
diff --git a/Polygon_mesh_processing/test/Polygon_mesh_processing/test_corefinement_and_constraints.cpp b/Polygon_mesh_processing/test/Polygon_mesh_processing/test_corefinement_and_constraints.cpp
index 3f3af6c44ae..7642f81f493 100644
--- a/Polygon_mesh_processing/test/Polygon_mesh_processing/test_corefinement_and_constraints.cpp
+++ b/Polygon_mesh_processing/test/Polygon_mesh_processing/test_corefinement_and_constraints.cpp
@@ -167,8 +167,8 @@ void test_bool_op_no_copy(
   typedef std::optional<Triangle_mesh*> OTM;
   Triangle_mesh *ptr = nullptr;
   const std::array<OTM,4> output =
-    reverse ? CGAL::make_array(OTM(&tm2), OTM(&tm1), std::make_optional(false,ptr), std::make_optional(false,ptr))
-            : CGAL::make_array(OTM(&tm1), OTM(&tm2), std::make_optional(false,ptr), std::make_optional(false,ptr));
+    reverse ? CGAL::make_array(OTM(&tm2), OTM(&tm1), std::optional<Triangle_mesh*>(), std::optional<Triangle_mesh*>())
+            : CGAL::make_array(OTM(&tm1), OTM(&tm2), std::optional<Triangle_mesh*>(), std::optional<Triangle_mesh*>());
   PMP::corefine_and_compute_boolean_operations(tm1,
                                                tm2,
                                                output,
diff --git a/Polyhedron/demo/Polyhedron/Plugins/PMP/Point_inside_polyhedron_plugin.cpp b/Polyhedron/demo/Polyhedron/Plugins/PMP/Point_inside_polyhedron_plugin.cpp
index a25fa8072f0..85238d26ff4 100644
--- a/Polyhedron/demo/Polyhedron/Plugins/PMP/Point_inside_polyhedron_plugin.cpp
+++ b/Polyhedron/demo/Polyhedron/Plugins/PMP/Point_inside_polyhedron_plugin.cpp
@@ -189,8 +189,7 @@ public Q_SLOTS:
   void on_Sample_random_points_from_bbox() {
 
     // calculate bbox of selected polyhedron items
-    std::optional<CGAL::Three::Scene_interface::Bbox> bbox
-      = std::make_optional(false, CGAL::Three::Scene_interface::Bbox());
+    std::optional<CGAL::Three::Scene_interface::Bbox> bbox;
     // Workaround a bug in g++-4.8.3:
     //   https://stackoverflow.com/a/21755207/1728537
     // Using std::make_optional to copy-initialize 'bbox' hides the
diff --git a/Polyhedron/demo/Polyhedron/Scene_polyhedron_selection_item.h b/Polyhedron/demo/Polyhedron/Scene_polyhedron_selection_item.h
index 15b6171cf28..a65e7adf764 100644
--- a/Polyhedron/demo/Polyhedron/Scene_polyhedron_selection_item.h
+++ b/Polyhedron/demo/Polyhedron/Scene_polyhedron_selection_item.h
@@ -295,9 +295,7 @@ public:
 
     constVPmap vpm = get(CGAL::vertex_point, *polyhedron());
 
-    std::optional<CGAL::Bbox_3> item_bbox
-      = std::make_optional(false, CGAL::Bbox_3());
-
+    std::optional<CGAL::Bbox_3> item_bbox;
 
     for(Selection_set_vertex::const_iterator v_it = selected_vertices.begin();
         v_it != selected_vertices.end(); ++v_it) {