diff --git a/src/bin/common_aoutput.cc b/src/bin/common_aoutput.cc
index 2312c1f52..8cabe4510 100644
--- a/src/bin/common_aoutput.cc
+++ b/src/bin/common_aoutput.cc
@@ -32,6 +32,7 @@
 #include "twaalgos/hoa.hh"
 #include "twaalgos/neverclaim.hh"
 #include "twaalgos/stutter.hh"
+#include "twaalgos/isunamb.hh"
 
 automaton_format_t automaton_format = Dot;
 static const char* opt_dot = nullptr;
@@ -42,11 +43,13 @@ static const char* opt_output = nullptr;
 static const char* stats = "";
 enum check_type
   {
-    check_stutter = (1 << 0),
+    check_unambiguous = (1 << 0),
+    check_stutter = (1 << 1),
     check_all = -1U,
   };
 static char const *const check_args[] =
   {
+    "unambiguous",
     "stutter-invariant", "stuttering-invariant",
     "stutter-insensitive", "stuttering-insensitive",
     "stutter-sensitive", "stuttering-sensitive",
@@ -55,6 +58,7 @@ static char const *const check_args[] =
   };
 static check_type const check_types[] =
   {
+    check_unambiguous,
     check_stutter, check_stutter,
     check_stutter, check_stutter,
     check_stutter, check_stutter,
@@ -115,7 +119,7 @@ static const argp_option options[] =
     { "check", OPT_CHECK, "PROP", OPTION_ARG_OPTIONAL,
       "test for the additional property PROP and output the result "
       "in the HOA format (implies -H).  PROP may be any prefix of "
-      "'all' (default), or 'stutter-invariant'.", 0 },
+      "'all' (default), 'unambiguous', or 'stutter-invariant'.", 0 },
     { 0, 0, 0, 0, 0, 0 }
   };
 
@@ -283,6 +287,8 @@ automaton_printer::print(const spot::twa_graph_ptr& aut,
     {
       if (opt_check & check_stutter)
 	check_stutter_invariance(aut, f);
+      if (opt_check & check_unambiguous)
+	spot::check_unambiguous(aut);
     }
 
   // Name the output automaton.
diff --git a/src/tests/unambig.test b/src/tests/unambig.test
index 0ca222fe2..4832519d3 100755
--- a/src/tests/unambig.test
+++ b/src/tests/unambig.test
@@ -35,6 +35,8 @@ for f in 'Ga' \
 do
   $ltl2tgba -UH "$f" | $autfilt -q --is-unambiguous
   $ltl2tgba -UH "!($f)" | $autfilt -q --is-unambiguous
+  $ltl2tgba -UH "$f" | $autfilt --check | grep unambiguous
+  $ltl2tgba -UH "!($f)" | $autfilt --check | grep unambiguous
 done
 
 for f in FGa
@@ -82,3 +84,5 @@ State: 1
 EOF
 
 run 1 $autfilt -q --is-unambiguous input
+run 0 $autfilt --check input > output
+test `grep -c unambiguous output` = 0
diff --git a/src/twa/twa.hh b/src/twa/twa.hh
index bb50212ec..4efee483f 100644
--- a/src/twa/twa.hh
+++ b/src/twa/twa.hh
@@ -715,6 +715,7 @@ namespace spot
       bool state_based_acc:1;	// State-based acceptance.
       bool inherently_weak:1;	// Weak automaton.
       bool deterministic:1;	// Deterministic automaton.
+      bool unambiguous:1;	// Unambiguous automaton.
       bool stutter_invariant:1;	// Stutter invariant language.
       bool stutter_sensitive:1;	// Stutter sensitive language.
     };
@@ -797,6 +798,16 @@ namespace spot
       is.deterministic = val;
     }
 
+    bool is_unambiguous() const
+    {
+      return is.unambiguous;
+    }
+
+    void prop_unambiguous(bool val = true)
+    {
+      is.unambiguous = val;
+    }
+
     bool is_stutter_invariant() const
     {
       return is.stutter_invariant;
@@ -839,7 +850,10 @@ namespace spot
       if (p.inherently_weak)
 	prop_inherently_weak(other->is_inherently_weak());
       if (p.deterministic)
-	prop_deterministic(other->is_deterministic());
+	{
+	  prop_deterministic(other->is_deterministic());
+	  prop_unambiguous(other->is_unambiguous());
+	}
       if (p.stutter_inv)
 	{
 	  prop_stutter_invariant(other->is_stutter_invariant());
@@ -854,7 +868,10 @@ namespace spot
       if (!p.inherently_weak)
 	prop_inherently_weak(false);
       if (!p.deterministic)
-	prop_deterministic(false);
+	{
+	  prop_deterministic(false);
+	  prop_unambiguous(false);
+	}
       if (!p.stutter_inv)
 	{
 	  prop_stutter_invariant(false);
diff --git a/src/twaalgos/hoa.cc b/src/twaalgos/hoa.cc
index 7068d0804..8e8922932 100644
--- a/src/twaalgos/hoa.cc
+++ b/src/twaalgos/hoa.cc
@@ -296,7 +296,6 @@ namespace spot
     os << aut->acc().get_acceptance();
     os << nl;
     os << "properties:";
-
     // Make sure the property line is not too large,
     // otherwise our test cases do not fit in 80 columns...
     unsigned prop_len = 60;
@@ -327,6 +326,8 @@ namespace spot
       prop(" complete");
     if (md.is_deterministic)
       prop(" deterministic");
+    if (aut->is_unambiguous())
+      prop(" unambiguous");
     assert(!(aut->is_stutter_invariant() && aut->is_stutter_sensitive()));
     if (aut->is_stutter_invariant())
       prop(" stutter-invariant");
diff --git a/src/twaalgos/isunamb.cc b/src/twaalgos/isunamb.cc
index 7584a23eb..3a22c1687 100644
--- a/src/twaalgos/isunamb.cc
+++ b/src/twaalgos/isunamb.cc
@@ -28,7 +28,7 @@ namespace spot
 {
   bool is_unambiguous(const const_twa_graph_ptr& aut)
   {
-    if (aut->is_deterministic())
+    if (aut->is_deterministic() || aut->is_unambiguous())
       return true;
     auto clean_a = scc_filter_states(aut);
     auto prod = product(clean_a, clean_a);
@@ -37,4 +37,10 @@ namespace spot
     tgba_statistics sp = stats_reachable(clean_p);
     return sa.states == sp.states && sa.transitions == sp.transitions;
   }
+
+  bool check_unambiguous(const twa_graph_ptr& aut)
+  {
+    aut->prop_unambiguous(is_unambiguous(aut));
+    return aut->is_unambiguous();
+  }
 }
diff --git a/src/twaalgos/isunamb.hh b/src/twaalgos/isunamb.hh
index 57f7c2a3f..1fca6fb8f 100644
--- a/src/twaalgos/isunamb.hh
+++ b/src/twaalgos/isunamb.hh
@@ -25,7 +25,7 @@ namespace spot
 {
   class tgba;
 
-  /// \addtogroup tgba_misc
+  /// \addtogroup twa_misc
   /// @{
 
   /// \brief Whether the automaton \a aut is unambiguous.
@@ -40,5 +40,8 @@ namespace spot
   SPOT_API bool
   is_unambiguous(const const_twa_graph_ptr& aut);
 
+  /// Like is_unambiguous(), but also sets the property in the twa.
+  SPOT_API bool
+  check_unambiguous(const twa_graph_ptr& aut);
   /// @}
 }
diff --git a/src/twaalgos/ltl2tgba_fm.cc b/src/twaalgos/ltl2tgba_fm.cc
index 74bce3595..add30de53 100644
--- a/src/twaalgos/ltl2tgba_fm.cc
+++ b/src/twaalgos/ltl2tgba_fm.cc
@@ -2555,6 +2555,9 @@ namespace spot
     a->prop_inherently_weak(f->is_syntactic_persistence());
     a->prop_stutter_invariant(f->is_syntactic_stutter_invariant());
 
+    // Currently the unambiguous option work only with LTL.
+    a->prop_unambiguous(f->is_ltl_formula() && unambiguous);
+
     if (!simplifier)
       // This should not be deleted before we have registered all propositions.
       delete s;