diff --git a/src/ltlast/unop.cc b/src/ltlast/unop.cc
index cd30b5609..5240cb2b9 100644
--- a/src/ltlast/unop.cc
+++ b/src/ltlast/unop.cc
@@ -1,8 +1,8 @@
-// Copyright (C) 2009, 2010 Laboratoire de Recherche et D�veloppement
+// Copyright (C) 2009, 2010 Laboratoire de Recherche et Développement
 // de l'Epita (LRDE).
 // Copyright (C) 2003, 2005 Laboratoire d'Informatique de Paris
-// 6 (LIP6), d�partement Syst�mes R�partis Coop�ratifs (SRC),
-// Universit� Pierre et Marie Curie.
+// 6 (LIP6), département Systèmes Répartis Coopératifs (SRC),
+// Université Pierre et Marie Curie.
 //
 // This file is part of Spot, a model checking library.
 //
@@ -101,6 +101,10 @@ namespace spot
 	  return "Finish";
 	case Star:
 	  return "Star";
+	case Closure:
+	  return "Closure";
+	case NegClosure:
+	  return "NegClosure";
 	}
       // Unreachable code.
       assert(0);
@@ -145,7 +149,7 @@ namespace spot
 	    if (child == constant::empty_word_instance())
 	      return constant::true_instance();
 	  }
-
+	  break;
 
 	case Not:
 	  {
@@ -155,13 +159,30 @@ namespace spot
 	    // !0 = 1
 	    if (child == constant::false_instance())
 	      return constant::true_instance();
-	    // Not is an involution.
 	    unop* u = dynamic_cast<unop*>(child);
-	    if (u && u->op() == op)
+	    if (u)
 	      {
-		formula* c = u->child()->clone();
-		u->destroy();
-		return c;
+		// "Not" is an involution.
+		if (u->op() == op)
+		  {
+		    formula* c = u->child()->clone();
+		    u->destroy();
+		    return c;
+		  }
+		if (u->op() == Closure)
+		  {
+		    formula* c = unop::instance(NegClosure,
+						u->child()->clone());
+		    u->destroy();
+		    return c;
+		  }
+		if (u->op() == NegClosure)
+		  {
+		    formula* c = unop::instance(Closure,
+						u->child()->clone());
+		    u->destroy();
+		    return c;
+		  }
 	      }
 	    break;
 	  }
@@ -179,6 +200,22 @@ namespace spot
 	case Finish:
 	  // No simplifications for Finish.
 	  break;
+
+	case Closure:
+	  if (child == constant::true_instance()
+	      || child == constant::empty_word_instance())
+	    return constant::true_instance();
+	  if (child == constant::false_instance())
+	    return child;
+	  break;
+
+	case NegClosure:
+	  if (child == constant::true_instance()
+	      || child == constant::empty_word_instance())
+	    return constant::false_instance();
+	  if (child == constant::false_instance())
+	    return constant::true_instance();
+	  break;
 	}
 
       pair p(op, child);
diff --git a/src/ltlast/unop.hh b/src/ltlast/unop.hh
index 5217fd108..2ac1ad471 100644
--- a/src/ltlast/unop.hh
+++ b/src/ltlast/unop.hh
@@ -1,8 +1,8 @@
-// Copyright (C) 2009, 2010 Laboratoire de Recherche et D�veloppement
+// Copyright (C) 2009, 2010 Laboratoire de Recherche et Développement
 // de l'Epita (LRDE).
 // Copyright (C) 2003, 2004 Laboratoire d'Informatique de Paris
-// 6 (LIP6), d�partement Syst�mes R�partis Coop�ratifs (SRC),
-// Universit� Pierre et Marie Curie.
+// 6 (LIP6), département Systèmes Répartis Coopératifs (SRC),
+// Université Pierre et Marie Curie.
 //
 // This file is part of Spot, a model checking library.
 //
@@ -47,6 +47,8 @@ namespace spot
 	Finish,
 	// Kleene Star
 	Star,
+	// Closure
+	Closure, NegClosure,
 	};
 
       /// \brief Build an unary operator with operation \a op and
@@ -69,6 +71,14 @@ namespace spot
       ///   - !1 = 0
       ///   - !0 = 1
       ///   - !!Exp = Exp
+      ///   - !Closure(Exp) = NegClosure(Exp)
+      ///   - !NegClosure(Exp) = Closure(Exp)
+      ///   - Closure(#e) = 1
+      ///   - Closure(1) = 1
+      ///   - Closure(0) = 0
+      ///   - NegClosure(#e) = 0
+      ///   - NegClosure(1) = 0
+      ///   - NegClosure(0) = 1
       ///
       /// This rewriting implies that it is not possible to build an
       /// LTL formula object that is SYNTACTICALLY equal to one of
diff --git a/src/ltlparse/ltlparse.yy b/src/ltlparse/ltlparse.yy
index 990a21670..c5da4b790 100644
--- a/src/ltlparse/ltlparse.yy
+++ b/src/ltlparse/ltlparse.yy
@@ -361,6 +361,8 @@ subformula: booleanatom
 	      { $$ = unop::instance(unop::Not, $2); }
 	    | OP_NOT error
 	      { missing_right_op($$, @1, "not operator"); }
+            | bracedrationalexp
+	      { $$ = unop::instance(unop::Closure, $1); }
             | bracedrationalexp OP_UCONCAT subformula
 	      { $$ = binop::instance(binop::UConcat, $1, $3); }
             | bracedrationalexp OP_UCONCAT error
@@ -369,6 +371,7 @@ subformula: booleanatom
 	      { $$ = binop::instance(binop::EConcat, $1, $3); }
             | bracedrationalexp OP_ECONCAT error
 	      { missing_right_binop($$, $1, @2, "universal concat operator"); }
+
 ;
 
 %%
diff --git a/src/ltlvisit/basicreduce.cc b/src/ltlvisit/basicreduce.cc
index 33e9ccdd8..58f91f9d0 100644
--- a/src/ltlvisit/basicreduce.cc
+++ b/src/ltlvisit/basicreduce.cc
@@ -239,11 +239,10 @@ namespace spot
 	      return;
 
 	    case unop::Finish:
-	      result_ = unop::instance(unop::Finish, result_);
-	      return;
-
 	    case unop::Star:
-	      result_ = unop::instance(unop::Star, result_);
+	    case unop::Closure:
+	    case unop::NegClosure:
+	      result_ = unop::instance(uo->op(), result_);
 	      return;
 	    }
 	  /* Unreachable code.  */
diff --git a/src/ltlvisit/consterm.cc b/src/ltlvisit/consterm.cc
index dae0ba8dd..afe78a93b 100644
--- a/src/ltlvisit/consterm.cc
+++ b/src/ltlvisit/consterm.cc
@@ -80,6 +80,8 @@ namespace spot
 	    case unop::F:
 	    case unop::G:
 	    case unop::Finish:
+	    case unop::Closure:
+	    case unop::NegClosure:
 	      assert(!"unsupported operator");
 	      break;
 	    case unop::Star:
diff --git a/src/ltlvisit/mark.cc b/src/ltlvisit/mark.cc
index 30608e7f6..d265a0c1a 100644
--- a/src/ltlvisit/mark.cc
+++ b/src/ltlvisit/mark.cc
@@ -59,8 +59,24 @@ namespace spot
 	}
 
 	void
-	visit(unop*)
+	visit(unop* uo)
 	{
+	  switch (uo->op())
+	    {
+	    case unop::NegClosure:
+	      result_ = true;
+	      return;
+	    case unop::Finish:
+	    case unop::Star:
+	    case unop::Closure:
+	    case unop::Not:
+	    case unop::X:
+	    case unop::F:
+	    case unop::G:
+	      return;
+	    }
+	  /* Unreachable code. */
+	  assert(0);
 	}
 
 	void
@@ -148,7 +164,23 @@ namespace spot
 	void
 	visit(unop* uo)
 	{
-	  result_ = uo->clone();
+	  switch (uo->op())
+	    {
+	    case unop::NegClosure:
+	      has_mark_ = true;
+	      /* fall through */
+	    case unop::Finish:
+	    case unop::Star:
+	    case unop::Closure:
+	    case unop::Not:
+	    case unop::X:
+	    case unop::F:
+	    case unop::G:
+	      result_ = uo->clone();
+	      return;
+	    }
+	  /* Unreachable code. */
+	  assert(0);
 	}
 
 	void
@@ -181,7 +213,9 @@ namespace spot
 
 		    binop* bo = dynamic_cast<binop*>(f);
 		    if (!bo)
-		      res->push_back(recurse(f));
+		      {
+			res->push_back(recurse(f));
+		      }
 		    else
 		      {
 			switch (bo->op())
@@ -317,7 +351,7 @@ namespace spot
 	    case binop::Xor:
 	    case binop::Implies:
 	    case binop::Equiv:
-	      assert(!"mark no defined on logic abbreviations");
+	      assert(!"mark not defined on logic abbreviations");
 	    case binop::U:
 	    case binop::W:
 	    case binop::M:
diff --git a/src/ltlvisit/nenoform.cc b/src/ltlvisit/nenoform.cc
index 3eb6573db..6a5f79fcb 100644
--- a/src/ltlvisit/nenoform.cc
+++ b/src/ltlvisit/nenoform.cc
@@ -108,15 +108,21 @@ namespace spot
 	      result_ = unop::instance(negated_ ? unop::F : unop::G,
 				       recurse(f));
 	      return;
-	    case unop::Finish:
-	      /* Finish(x) is not simplified */
-	      result_ = unop::instance(unop::Finish, recurse_(f, false));
-	      if (negated_)
-		result_ = unop::instance(unop::Not, result_);
+	    case unop::Closure:
+	      result_ = unop::instance(negated_ ?
+				       unop::NegClosure : unop::Closure,
+				       recurse_(f, false));
 	      return;
-	    case unop::Star:
+	    case unop::NegClosure:
+	      result_ = unop::instance(negated_ ?
+				       unop::Closure : uo->op(),
+				       recurse_(f, false));
+	      return;
+	      /* !Finish(x), is not simplified */
 	      /* !(a*) is not simplified */
-	      result_ = unop::instance(unop::Star, recurse_(f, false));
+	    case unop::Finish:
+	    case unop::Star:
+	      result_ = unop::instance(uo->op(), recurse_(f, false));
 	      if (negated_)
 		result_ = unop::instance(unop::Not, result_);
 	      return;
diff --git a/src/ltlvisit/reduce.cc b/src/ltlvisit/reduce.cc
index 1c5974611..330a8bc0a 100644
--- a/src/ltlvisit/reduce.cc
+++ b/src/ltlvisit/reduce.cc
@@ -235,14 +235,6 @@ namespace spot
 
 	  switch (uo->op())
 	    {
-	    case unop::Not:
-	      result_ = unop::instance(unop::Not, result_);
-	      return;
-
-	    case unop::X:
-	      result_ = unop::instance(unop::X, result_);
-	      return;
-
 	    case unop::F:
 	      /* If f is a pure eventuality formula then F(f)=f.  */
 	      if (!(opt_ & Reduce_Eventuality_And_Universality)
@@ -257,14 +249,14 @@ namespace spot
 		result_ = unop::instance(unop::G, result_);
 	      return;
 
+	    case unop::Not:
+	    case unop::X:
 	    case unop::Finish:
-	      result_ = unop::instance(unop::Finish, result_);
-	      return;
-
 	    case unop::Star:
-	      result_ = unop::instance(unop::Star, result_);
+	    case unop::Closure:
+	    case unop::NegClosure:
+	      result_ = unop::instance(uo->op(), result_);
 	      return;
-
 	    }
 	  /* Unreachable code.  */
 	  assert(0);
diff --git a/src/ltlvisit/syntimpl.cc b/src/ltlvisit/syntimpl.cc
index 9c0e2b32d..8cda46119 100644
--- a/src/ltlvisit/syntimpl.cc
+++ b/src/ltlvisit/syntimpl.cc
@@ -106,8 +106,9 @@ namespace spot
 		result_ = true;
 	      return;
 	    case unop::Finish:
-	      return;
 	    case unop::Star:
+	    case unop::Closure:
+	    case unop::NegClosure:
 	      return;
 	    }
 	  /* Unreachable code.  */
@@ -337,8 +338,9 @@ namespace spot
 		return;
 	      }
 	    case unop::Finish:
-	      return;
 	    case unop::Star:
+	    case unop::Closure:
+	    case unop::NegClosure:
 	      return;
 	    }
 	  /* Unreachable code.  */
diff --git a/src/ltlvisit/tostring.cc b/src/ltlvisit/tostring.cc
index 2e53948e4..9e7f008c0 100644
--- a/src/ltlvisit/tostring.cc
+++ b/src/ltlvisit/tostring.cc
@@ -164,6 +164,7 @@ namespace spot
 	void
 	visit(const unop* uo)
 	{
+	  top_level_ = false;
 	  // The parser treats F0, F1, G0, G1, X0, and X1 as atomic
 	  // propositions.  So make sure we output F(0), G(1), etc.
 	  bool need_parent = !!dynamic_cast<const constant*>(uo->child());
@@ -196,24 +197,43 @@ namespace spot
 	      os_ << "finish";
 	      need_parent = true;
 	      break;
+	    case unop::Closure:
+	      os_ << "{";
+	      top_level_ = true;
+	      break;
+	    case unop::NegClosure:
+	      os_ << "!{";
+	      break;
 	    case unop::Star:
-	      // Do not output anything yet, star is a postfix operator.
+	      // 1* is OK, no need to print (1)*.
 	      need_parent = false;
+	      // Do not output anything yet, star is a postfix operator.
 	      break;
 	    }
 
 	  top_level_ = false;
-	  if (need_parent)
+	  if (need_parent || full_parent_)
 	    os_ << "(";
 	  uo->child()->accept(*this);
 	  if (need_parent)
 	    os_ << ")";
 
+	  switch (uo->op())
+	    {
+	    case unop::Star:
+	      os_ << "*";
+	      break;
+	    case unop::Closure:
+	    case unop::NegClosure:
+	      os_ << "}";
+	      top_level_ = false;
+	      break;
+	    default:
+	      break;
+	    }
+
 	  if (full_parent_ && !top_level)
 	    os_ << ")";
-
-	  if (uo->op() == unop::Star)
-	    os_ << "*";
 	}
 
 	void
@@ -377,15 +397,17 @@ namespace spot
 	  bool top_level = top_level_;
 	  if (full_parent_ && !top_level)
 	    os_ << "(";
+
 	  bool need_parent = false;
+	  top_level_ = false;
 	  switch (uo->op())
 	    {
 	    case unop::Not:
 	      os_ << "!";
 	      break;
 	    case unop::X:
-	      // The parser treats X0, and X1 as atomic propositions.	 So
-	      // make sure we output X(0) and X(1).
+	      // The parser treats X0, and X1 as atomic
+	      // propositions. So make sure we output X(0) and X(1).
 	      need_parent = !!dynamic_cast<const constant*>(uo->child());
 	      if (full_parent_)
 		need_parent = false;
@@ -401,14 +423,19 @@ namespace spot
 	      os_ << "finish";
 	      need_parent = true;
 	      break;
+	    case unop::Closure:
+	      os_ << "{";
+	      top_level_ = true;
+	      break;
+	    case unop::NegClosure:
+	      os_ << "!{";
+	      top_level_ = true;
+	      break;
 	    case unop::Star:
 	      // Do not output anything yet, star is a postfix operator.
-	      // FIXME: is there a better way to output "Star" for Spin?
-	      need_parent = false;
 	      break;
 	    }
 
-	  top_level_ = false;
 	  if (need_parent)
 	    os_ << "(";
 	  uo->child()->accept(*this);
@@ -416,6 +443,21 @@ namespace spot
 	    os_ << ")";
 	  if (uo->op() == unop::Star)
 	    os_ << "*";
+
+	  switch (uo->op())
+	    {
+	    case unop::Star:
+	      os_ << "*";
+	      break;
+	    case unop::Closure:
+	    case unop::NegClosure:
+	      os_ << "}";
+	      top_level_ = false;
+	      break;
+	    default:
+	      break;
+	    }
+
 	  if (full_parent_ && !top_level)
 	    os_ << ")";
 	}
diff --git a/src/ltlvisit/tunabbrev.cc b/src/ltlvisit/tunabbrev.cc
index 6f8485380..e12dbc464 100644
--- a/src/ltlvisit/tunabbrev.cc
+++ b/src/ltlvisit/tunabbrev.cc
@@ -1,4 +1,6 @@
-// Copyright (C) 2003, 2009  Laboratoire d'Informatique de Paris 6 (LIP6),
+// Copyright (C) 2009, 2010 Laboratoire de Recherche et Développement
+// de l'Epita (LRDE).
+// Copyright (C) 2003  Laboratoire d'Informatique de Paris 6 (LIP6),
 // département Systèmes Répartis Coopératifs (SRC), Université Pierre
 // et Marie Curie.
 //
@@ -43,6 +45,8 @@ namespace spot
 	case unop::X:
 	case unop::Not:
 	case unop::Star:
+	case unop::Closure:
+	case unop::NegClosure:
 	  this->super::visit(uo);
 	  return;
 	case unop::F:
diff --git a/src/tgba/formula2bdd.cc b/src/tgba/formula2bdd.cc
index 7b4959da9..09181e285 100644
--- a/src/tgba/formula2bdd.cc
+++ b/src/tgba/formula2bdd.cc
@@ -80,6 +80,8 @@ namespace spot
 	  case unop::G:
 	  case unop::X:
 	  case unop::Star:
+	  case unop::Closure:
+	  case unop::NegClosure:
 	    assert(!"unsupported operator");
 	  case unop::Not:
 	    {
diff --git a/src/tgbaalgos/eltl2tgba_lacim.cc b/src/tgbaalgos/eltl2tgba_lacim.cc
index 6804bf241..80c23b967 100644
--- a/src/tgbaalgos/eltl2tgba_lacim.cc
+++ b/src/tgbaalgos/eltl2tgba_lacim.cc
@@ -102,6 +102,8 @@ namespace spot
 	  case unop::F:
           case unop::G:
 	  case unop::Star:
+	  case unop::Closure:
+	  case unop::NegClosure:
 	    assert(!"unsupported operator");
 	  }
 	/* Unreachable code.  */
diff --git a/src/tgbaalgos/ltl2taa.cc b/src/tgbaalgos/ltl2taa.cc
index 4b7b33704..c06e81fe9 100644
--- a/src/tgbaalgos/ltl2taa.cc
+++ b/src/tgbaalgos/ltl2taa.cc
@@ -142,6 +142,8 @@ namespace spot
 	    return;
 	  case unop::Finish:
 	  case unop::Star:
+	  case unop::Closure:
+	  case unop::NegClosure:
 	    assert(!"unsupported operator");
 	    return;
 	}
diff --git a/src/tgbaalgos/ltl2tgba_fm.cc b/src/tgbaalgos/ltl2tgba_fm.cc
index 9adc18246..94ee54a80 100644
--- a/src/tgbaalgos/ltl2tgba_fm.cc
+++ b/src/tgbaalgos/ltl2tgba_fm.cc
@@ -240,9 +240,10 @@ namespace spot
 	  bdd label = bdd_exist(cube, d.next_set);
 	  bdd dest_bdd = bdd_existcomp(cube, d.next_set);
 	  const formula* dest = d.conj_bdd_to_formula(dest_bdd);
-	  bdd_print_set(std::cerr, d.dict, label) << " => "
-						  << to_string(dest)
-						  << std::endl;
+	  bdd_print_set(std::cerr, d.dict, label) << " => ";
+	  bdd_print_set(std::cerr, d.dict, dest_bdd) << " = "
+						     << to_string(dest)
+						     << std::endl;
 	  dest->destroy();
 	}
       return std::cerr;
@@ -297,8 +298,11 @@ namespace spot
     {
     public:
       ratexp_trad_visitor(translate_dict& dict,
+			  bool empty_word_is_true,
 			  formula* to_concat = 0)
-	: dict_(dict), to_concat_(to_concat)
+	: dict_(dict),
+	  empty_word_is_true_(empty_word_is_true),
+	  to_concat_(to_concat)
       {
       }
 
@@ -325,17 +329,10 @@ namespace spot
 
       bdd now_to_concat()
       {
-	if (to_concat_)
-	  {
-	    if (to_concat_ == constant::empty_word_instance())
-	      return bddfalse;
-	    bdd n = recurse(to_concat_);
-	    return n;
-	  }
-	else
-	  {
-	    return bddfalse;
-	  }
+	if (to_concat_ && to_concat_ != constant::empty_word_instance())
+	  return recurse(to_concat_);
+
+	return empty_word_is_true_ ? bddtrue : bddfalse;
       }
 
       void
@@ -374,6 +371,9 @@ namespace spot
 	  case unop::Not:
 	  case unop::X:
 	  case unop::Finish:
+	  case unop::Closure:
+	  case unop::NegClosure:
+	    break;
 	    assert(!"not a rational operator");
 	    return;
 	  case unop::Star:
@@ -556,7 +556,7 @@ namespace spot
       bdd
       recurse(const formula* f, formula* to_concat = 0)
       {
-	ratexp_trad_visitor v(dict_, to_concat);
+	ratexp_trad_visitor v(dict_, empty_word_is_true_, to_concat);
 	f->accept(v);
 	return v.result();
       }
@@ -565,6 +565,7 @@ namespace spot
     private:
       translate_dict& dict_;
       bdd res_;
+      bool empty_word_is_true_;
       formula* to_concat_;
     };
 
@@ -646,7 +647,9 @@ namespace spot
       void
       visit(const unop* node)
       {
-	switch (node->op())
+	unop::type op = node->op();
+
+	switch (op)
 	  {
 	  case unop::F:
 	    {
@@ -691,6 +694,120 @@ namespace spot
 	      res_ = bdd_ithvar(x);
 	      break;
 	    }
+	  case unop::Closure:
+	    {
+	      rat_seen_ = true;
+	      ratexp_trad_visitor v(dict_, true);
+	      node->child()->accept(v);
+	      bdd f1 = v.result();
+	      res_ = bddfalse;
+
+	      if (exprop_)
+		{
+		  bdd var_set = bdd_existcomp(bdd_support(f1), dict_.var_set);
+		  bdd all_props = bdd_existcomp(f1, dict_.var_set);
+		  while (all_props != bddfalse)
+		    {
+		      bdd label = bdd_satoneset(all_props, var_set, bddtrue);
+		      all_props -= label;
+
+		      formula* dest =
+			dict_.bdd_to_formula(bdd_exist(f1 & label,
+						       dict_.var_set));
+
+		      const formula* dest2;
+		      if (constant_term_as_bool(dest))
+			{
+			  dest->destroy();
+			  res_ |= label;
+			}
+		      else
+			{
+			  dest2 = unop::instance(op, dest);
+			  if (dest2 == constant::false_instance())
+			    continue;
+			  int x = dict_.register_next_variable(dest2);
+			  dest2->destroy();
+			  res_ |= label & bdd_ithvar(x);
+			}
+		    }
+		}
+	      else
+		{
+		  minato_isop isop(f1);
+		  bdd cube;
+		  while ((cube = isop.next()) != bddfalse)
+		    {
+		      bdd label = bdd_exist(cube, dict_.next_set);
+		      bdd dest_bdd = bdd_existcomp(cube, dict_.next_set);
+		      formula* dest = dict_.conj_bdd_to_formula(dest_bdd);
+
+		      const formula* dest2;
+		      if (constant_term_as_bool(dest))
+			{
+			  dest->destroy();
+			  res_ |= label;
+			}
+		      else
+			{
+			  dest2 = unop::instance(op, dest);
+			  if (dest2 == constant::false_instance())
+			    continue;
+			  int x = dict_.register_next_variable(dest2);
+			  dest2->destroy();
+			  res_ |= label & bdd_ithvar(x);
+			}
+		    }
+		}
+	    }
+	    break;
+
+	  case unop::NegClosure:
+	    {
+	      rat_seen_ = true;
+	      has_marked_ = true;
+	      ratexp_trad_visitor v(dict_, true);
+	      node->child()->accept(v);
+	      bdd f1 = v.result();
+
+	      // trace_ltl_bdd(dict_, f1);
+
+	      bdd var_set = bdd_existcomp(bdd_support(f1), dict_.var_set);
+	      bdd all_props = bdd_existcomp(f1, dict_.var_set);
+
+	      res_ = !all_props &
+		// stick X(1) to preserve determinism.
+		bdd_ithvar(dict_.register_next_variable
+			   (constant::true_instance()));
+
+	      while (all_props != bddfalse)
+		{
+		  bdd label = bdd_satoneset(all_props, var_set, bddtrue);
+		  all_props -= label;
+
+		  formula* dest =
+		    dict_.bdd_to_formula(bdd_exist(f1 & label,
+						   dict_.var_set));
+
+		  // !{ Exp } is false if Exp accepts the empty word.
+		  if (constant_term_as_bool(dest))
+		    {
+		      dest->destroy();
+		      continue;
+		    }
+
+		  const formula* dest2 = unop::instance(op, dest);
+
+		  if (dest == constant::false_instance())
+		    continue;
+
+		  int x = dict_.register_next_variable(dest2);
+		  dest2->destroy();
+		  res_ |= label & bdd_ithvar(x);
+		}
+	    }
+	    break;
+
 	  case unop::Finish:
 	    assert(!"unsupported operator");
 	    break;
@@ -776,7 +893,7 @@ namespace spot
 	      // Recognize f2 on transitions going to destinations
 	      // that accept the empty word.
 	      bdd f2 = recurse(node->second());
-	      ratexp_trad_visitor v(dict_);
+	      ratexp_trad_visitor v(dict_, false);
 	      node->first()->accept(v);
 	      bdd f1 = v.result();
 	      res_ = bddfalse;
@@ -851,7 +968,7 @@ namespace spot
 	      // word should recognize f2, and the automaton for f1
 	      // should be understood as universal.
 	      bdd f2 = recurse(node->second());
-	      ratexp_trad_visitor v(dict_);
+	      ratexp_trad_visitor v(dict_, false);
 	      node->first()->accept(v);
 	      bdd f1 = v.result();
 	      res_ = bddtrue;
@@ -931,10 +1048,13 @@ namespace spot
 	      for (unsigned n = 0; n < s; ++n)
 		{
 		  bdd res = recurse(node->nth(n));
-		  //std::cerr << "=== in And" << std::endl;
-		  //trace_ltl_bdd(dict_, res);
+		  //std::cerr << "== in And (" << to_string(node->nth(n))
+		  // << ")" << std::endl;
+		  // trace_ltl_bdd(dict_, res);
 		  res_ &= res;
 		}
+	      //std::cerr << "=== And final" << std::endl;
+	      // trace_ltl_bdd(dict_, res_);
 	      break;
 	    }
 	  case multop::Or:
diff --git a/src/tgbaalgos/ltl2tgba_lacim.cc b/src/tgbaalgos/ltl2tgba_lacim.cc
index ad7323f3e..2b629b877 100644
--- a/src/tgbaalgos/ltl2tgba_lacim.cc
+++ b/src/tgbaalgos/ltl2tgba_lacim.cc
@@ -151,6 +151,8 @@ namespace spot
 	    }
 	  case unop::Finish:
 	  case unop::Star:
+	  case unop::Closure:
+	  case unop::NegClosure:
 	    assert(!"unsupported operator");
 	  }
 	/* Unreachable code.  */
diff --git a/src/tgbatest/ltl2tgba.test b/src/tgbatest/ltl2tgba.test
index 339a16c45..0b535b7e3 100755
--- a/src/tgbatest/ltl2tgba.test
+++ b/src/tgbatest/ltl2tgba.test
@@ -70,6 +70,16 @@ check_psl 'G({(a;b)*}<>->x)&G({(c;d)*}<>->y)'
 check_psl '{(#e + a):c*:(#e + b)}<>->d'
 check_psl '{a;e;f:(g*);h}<>->d'
 check_psl '{(a:b)* & (c*:d)}<>->e'
+check_psl '{(a:b)*}'
+check_psl 'G{(a:b)*}'
+check_psl '{a;b}'
+check_psl '{(a;b)*}'
+check_psl 'G{(a;b)*}'
+check_psl '{a*}[]->{b*}'
+
+# Example from "Beyond Hardware Verification" by Glazberg, Moulin, Orni,
+# Ruah, Zarpas (2007).
+check_psl '{1*;req;ack;1}[]->{start;busy*;done}'
 
 # Make sure 'a U (b U c)' has 3 states and 6 transitions,
 # before and after degeneralization.