diff --git a/spot/twaalgos/gfguarantee.cc b/spot/twaalgos/gfguarantee.cc
index 94496ee6e..f0aa58274 100644
--- a/spot/twaalgos/gfguarantee.cc
+++ b/spot/twaalgos/gfguarantee.cc
@@ -260,7 +260,7 @@ namespace spot
                       // history further.
                       if (hlen > 0)
                         for (auto& ei: aut->out(moved_init))
-                          if ((ei.cond & econd) != bddfalse
+                          if (bdd_have_common_assignment(ei.cond, econd)
                               && term[si.scc_of(ei.dst)])
                             goto failed;
 
diff --git a/spot/twaalgos/isdet.cc b/spot/twaalgos/isdet.cc
index b7b6df0be..864a9315c 100644
--- a/spot/twaalgos/isdet.cc
+++ b/spot/twaalgos/isdet.cc
@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2012-2018 Laboratoire de Recherche et Développement
+// Copyright (C) 2012-2018, 2021 Laboratoire de Recherche et Développement
 // de l'Epita (LRDE).
 //
 // This file is part of Spot, a model checking library.
@@ -132,7 +132,7 @@ namespace spot
         // Second pass to gather the relevant edges.
         if (!universal)
           for (auto& t: aut->out(src))
-            if ((t.cond & extra) != bddfalse)
+            if (bdd_have_common_assignment(t.cond, extra))
               (*highlight)[aut->get_graph().index_of_edge(t)] = color;
       }
     aut->prop_universal(universal);