diff --git a/src/bin/autfilt.cc b/src/bin/autfilt.cc
index b8b26f7f0..40e323da7 100644
--- a/src/bin/autfilt.cc
+++ b/src/bin/autfilt.cc
@@ -77,7 +77,6 @@ Exit status:\n\
 #define OPT_DESTUT 22
 #define OPT_INSTUT 23
 #define OPT_IS_EMPTY 24
-#define OPT_UNIQ 25
 
 static const argp_option options[] =
   {
@@ -164,7 +163,7 @@ static const argp_option options[] =
     { 0, 0, 0, 0, "Filters:", 6 },
     { "are-isomorphic", OPT_ARE_ISOMORPHIC, "FILENAME", 0,
       "keep automata that are isomorphic to the automaton in FILENAME", 0 },
-    { "uniq", OPT_UNIQ, 0, 0,
+    { "uniq", 'u', 0, 0,
       "do not output the same automaton twice (same in the sense that they "\
       "are isomorphic)", 0 },
     { "isomorphic", 0, 0, OPTION_ALIAS | OPTION_HIDDEN, 0, 0 },
@@ -279,6 +278,10 @@ parse_opt(int key, char* arg, struct argp_state*)
       if (type != spot::postprocessor::Monitor)
 	type = spot::postprocessor::BA;
       break;
+    case 'u':
+      opt_uniq =
+        std::unique_ptr<unique_aut_t>(new std::set<std::vector<tr_t>>());
+      break;
     case 'v':
       opt_invert = true;
       break;
@@ -401,10 +404,6 @@ parse_opt(int key, char* arg, struct argp_state*)
 	error(2, 0, "--spin and --tgba are incompatible");
       type = spot::postprocessor::TGBA;
       break;
-    case OPT_UNIQ:
-      opt_uniq =
-        std::unique_ptr<unique_aut_t>(new std::set<std::vector<tr_t>>());
-      break;
     case ARGP_KEY_ARG:
       jobs.emplace_back(arg, true);
       break;
@@ -470,14 +469,6 @@ namespace
         matched &= isomorphism_checker->is_isomorphic(aut);
       if (opt_is_empty)
 	matched &= aut->is_empty();
-      if (opt_uniq)
-        {
-          auto tmp =
-	    spot::canonicalize(make_tgba_digraph(aut,
-						 spot::tgba::prop_set::all()));
-          matched = opt_uniq->emplace(tmp->transition_vector().begin() + 1,
-                                      tmp->transition_vector().end()).second;
-        }
 
       // Drop or keep matched automata depending on the --invert option
       if (matched == opt_invert)
@@ -502,6 +493,16 @@ namespace
 
       const double conversion_time = sw.stop();
 
+      if (opt_uniq)
+        {
+          auto tmp =
+	    spot::canonicalize(make_tgba_digraph(aut,
+						 spot::tgba::prop_set::all()));
+          if (!opt_uniq->emplace(tmp->transition_vector().begin() + 1,
+				 tmp->transition_vector().end()).second)
+	    return 0;
+        }
+
       printer.print(aut, filename, conversion_time, haut);
 
       if (opt_max_count >= 0 && match_count >= opt_max_count)
diff --git a/src/bin/randaut.cc b/src/bin/randaut.cc
index 37e79d14e..1e0d08c41 100644
--- a/src/bin/randaut.cc
+++ b/src/bin/randaut.cc
@@ -67,7 +67,6 @@ states, 1 to 3 acceptance sets, and three atomic propositions:\n\
 #define OPT_LBTT 3
 #define OPT_SEED 4
 #define OPT_STATE_ACC 5
-#define OPT_UNIQ 6
 
 static const argp_option options[] =
   {
@@ -83,7 +82,7 @@ static const argp_option options[] =
     { "density", 'd', "FLOAT", 0, "density of the transitions (0.2)", 0 },
     { "deterministic", 'D', 0, 0, "build a complete, deterministic automaton ",
       0 },
-    { "uniq", OPT_UNIQ, 0, 0,
+    { "uniq", 'u', 0, 0,
       "do not output the same automaton twice (same in the sense that they "\
       "are isomorphic)", 0 },
     { "seed", OPT_SEED, "INT", 0,
@@ -212,6 +211,10 @@ parse_opt(int key, char* arg, struct argp_state* as)
       if (opt_states.min > opt_states.max)
 	std::swap(opt_states.min, opt_states.max);
       break;
+    case 'u':
+      opt_uniq =
+        std::unique_ptr<unique_aut_t>(new std::set<std::vector<tr_t>>());
+      break;
     case OPT_DOT:
       format = Dot;
       opt_dot = arg;
@@ -235,9 +238,6 @@ parse_opt(int key, char* arg, struct argp_state* as)
     case OPT_STATE_ACC:
       opt_state_acc = true;
       break;
-    case OPT_UNIQ:
-      opt_uniq =
-        std::unique_ptr<unique_aut_t>(new std::set<std::vector<tr_t>>());
     case ARGP_KEY_ARG:
       // If this is the unique non-option argument, it can
       // be a number of atomic propositions to build.
@@ -294,7 +294,10 @@ main(int argc, char** argv)
   spot::srand(opt_seed);
   auto d = spot::make_bdd_dict();
 
-  while (opt_automata < 0 || opt_automata--)
+  constexpr unsigned max_trials = 10000;
+  unsigned trials = max_trials;
+
+  while (opt_automata)
     {
       int size = opt_states.min;
       if (size != opt_states.max)
@@ -316,10 +319,20 @@ main(int argc, char** argv)
 						 spot::tgba::prop_set::all()));
           std::vector<tr_t> trans(tmp->transition_vector().begin() + 1,
                                   tmp->transition_vector().end());
-          if (opt_uniq->emplace(trans).second)
-            return 0;
+          if (!opt_uniq->emplace(trans).second)
+	    {
+	      --trials;
+	      if (trials == 0)
+		error(2, 0, "failed to generate a new unique automaton"
+		      " after %d trials", max_trials);
+	      continue;
+	    }
+	  trials = max_trials;
         }
 
+      if (opt_automata > 0)
+	--opt_automata;
+
       bool is_ba = accs == 0 || (accs == 1 && opt_state_acc);
 
       switch (format)
diff --git a/src/tgbatest/uniq.test b/src/tgbatest/uniq.test
index 91915a3c1..779feb5fc 100755
--- a/src/tgbatest/uniq.test
+++ b/src/tgbatest/uniq.test
@@ -33,3 +33,21 @@ cat aut1 aut2 > aut
 cat aut1 aut2 rand11 rand12 rand13 rand21 rand22 rand23 > all
 ../../bin/autfilt all --uniq --hoa > out
 diff aut out
+
+
+run 0 ../../bin/randaut -Hl -u -n 4 -S1 a b | sort |
+      ../../bin/autfilt -H | grep '&' > out
+cat >expected <<EOF
+[!0&!1] 0
+[!0&1] 0
+[0&!1] 0
+[0&1] 0
+EOF
+diff out expected
+
+# This should fail: the random automaton generator can only generate 4
+# different one-state automaton with two atomic propositions.
+../../bin/randaut -Hl -u -n 5 -S1 a b >out 2>stderr && exit 1
+test $? = 2
+grep 'failed to generate a new unique automaton' stderr
+test 4 = `wc -l < out`