diff --git a/spot/twacube/cube.cc b/spot/twacube/cube.cc
index 10f13f8db..d0c426b0c 100644
--- a/spot/twacube/cube.cc
+++ b/spot/twacube/cube.cc
@@ -34,9 +34,6 @@ namespace spot
       ++uint_size_;
   }
 
-  cubeset::~cubeset()
-  { }
-
   cube cubeset::alloc() const
   {
     auto* res = new unsigned int[2*uint_size_];
diff --git a/spot/twacube/cube.hh b/spot/twacube/cube.hh
index 6dda9c9e8..dcdecf6ab 100644
--- a/spot/twacube/cube.hh
+++ b/spot/twacube/cube.hh
@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2015, 2016 Laboratoire de Recherche et Developpement de
+// Copyright (C) 2015, 2016, 2018 Laboratoire de Recherche et Developpement de
 // l'Epita (LRDE).
 //
 // This file is part of Spot, a model checking library.
@@ -77,14 +77,13 @@ namespace spot
     size_t nb_bits_;
 
   public:
-    // Some deleted constructor
+    // Some default/deleted constructor/destructors
     cubeset() = delete;
+    ~cubeset() = default;
 
     /// \brief Build the cubeset manager for \a aps variables
     cubeset(int aps);
 
-    virtual ~cubeset();
-
     /// \brief Allocate a new cube
     cube alloc() const;
 
diff --git a/spot/twacube/twacube.cc b/spot/twacube/twacube.cc
index 563698e92..26b4342d6 100644
--- a/spot/twacube/twacube.cc
+++ b/spot/twacube/twacube.cc
@@ -30,9 +30,6 @@ namespace spot
   {
   }
 
-  cstate::~cstate()
-  { }
-
   unsigned cstate::label()
   {
     return id_;
@@ -47,12 +44,6 @@ namespace spot
     cube_(cube),  acc_(acc)
   { }
 
-  transition::~transition()
-  { }
-
-  transition::transition()
-  { }
-
   twacube::twacube(const std::vector<std::string> aps):
     init_(0U), aps_(aps), cubeset_(aps.size())
   {
@@ -60,7 +51,7 @@ namespace spot
 
   twacube::~twacube()
   {
-    spot::cubeset cs = get_cubeset();
+    const spot::cubeset cs = get_cubeset();
     for (unsigned i = 1; i <= theg_.num_edges(); ++i)
       cs.release(theg_.edge_data(i).cube_);
   }
diff --git a/spot/twacube/twacube.hh b/spot/twacube/twacube.hh
index f35917265..0769b3e09 100644
--- a/spot/twacube/twacube.hh
+++ b/spot/twacube/twacube.hh
@@ -33,11 +33,12 @@ namespace spot
   class SPOT_API cstate
   {
   public:
-    cstate() {}
+    cstate() = default;
     cstate(const cstate& s) = delete;
     cstate(cstate&& s) noexcept;
     cstate(unsigned id);
-    virtual ~cstate();
+    ~cstate() = default;
+
     unsigned label();
   private:
     unsigned id_;
@@ -47,13 +48,14 @@ namespace spot
   class SPOT_API transition
   {
   public:
-    cube cube_;
-    acc_cond::mark_t acc_;
-    transition();
+    transition() = default;
     transition(const transition& t) = delete;
     transition(transition&& t) noexcept;
     transition(const cube& cube, acc_cond::mark_t acc);
-    virtual ~transition();
+    ~transition() = default;
+
+    cube cube_;
+    acc_cond::mark_t acc_;
   };
 
   /// \brief Class for iterators over transitions
@@ -119,7 +121,7 @@ namespace spot
     const graph_t::state_storage_t& st_; ///< The underlying states
   };
 
-  /// \brief Class for representign
+  /// \brief Class for representing a thread-safe twa.
   class SPOT_API twacube final: public std::enable_shared_from_this<twacube>
   {
   public: