diff --git a/spot/twaalgos/alternation.cc b/spot/twaalgos/alternation.cc
index d5d59a961..03b8d5c2a 100644
--- a/spot/twaalgos/alternation.cc
+++ b/spot/twaalgos/alternation.cc
@@ -38,7 +38,7 @@ namespace spot
     aut_->get_dict()->unregister_all_my_variables(this);
   }
 
-  bdd outedge_combiner::operator()(unsigned st)
+  bdd outedge_combiner::operator()(unsigned st, const std::vector<unsigned>& dst_filter)
   {
     const auto& dict = aut_->get_dict();
     bdd res = bddtrue;
@@ -47,6 +47,21 @@ namespace spot
         bdd res2 = bddfalse;
         for (auto& e: aut_->out(d1))
           {
+            // handle edge filtering
+            if (!dst_filter.empty())
+              {
+                // if any edge destination is an accepting state in the SERE
+                // automaton, handle the edge, otherwise skip it
+                auto univ_dests = aut_->univ_dests(e.dst);
+                if (std::all_of(univ_dests.begin(), univ_dests.end(),
+                                [&](unsigned dst)
+                                {
+                                  return std::find(dst_filter.begin(), dst_filter.end(), dst)
+                                    == dst_filter.end();
+                                }))
+                  continue;
+              }
+
             bdd out = bddtrue;
             for (unsigned d: aut_->univ_dests(e.dst))
               {
@@ -65,7 +80,9 @@ namespace spot
               }
             res2 |= e.cond & out;
           }
-        res &= res2;
+
+        if (res2 != bddfalse)
+          res &= res2;
       }
     return res;
   }
diff --git a/spot/twaalgos/alternation.hh b/spot/twaalgos/alternation.hh
index 9490272a1..4949006f2 100644
--- a/spot/twaalgos/alternation.hh
+++ b/spot/twaalgos/alternation.hh
@@ -53,7 +53,7 @@ namespace spot
   public:
     outedge_combiner(const twa_graph_ptr& aut, unsigned sink = -1u);
     ~outedge_combiner();
-    bdd operator()(unsigned st);
+    bdd operator()(unsigned st, const std::vector<unsigned>& dst_filter = std::vector<unsigned>());
     void new_dests(unsigned st, bdd out) const;
   };
 
diff --git a/spot/twaalgos/translate_aa.cc b/spot/twaalgos/translate_aa.cc
index daf9126cb..11b783691 100644
--- a/spot/twaalgos/translate_aa.cc
+++ b/spot/twaalgos/translate_aa.cc
@@ -274,8 +274,7 @@ namespace spot
 
           case op::UConcat:
           {
-            // FIXME: combine out edges with rhs !
-            //unsigned rhs_init = recurse(f[1]);
+            unsigned rhs_init = recurse(f[1]);
             const auto& dict = aut_->get_dict();
             twa_graph_ptr sere_aut = derive_finite_automaton_with_first(f[0], dict);
 
@@ -286,6 +285,7 @@ namespace spot
             bdd vars = bddtrue;
             bdd aps = sere_aut->ap_vars();
             std::vector<unsigned> univ_dest;
+            std::vector<unsigned> acc_states;
 
             // registers a state in various maps and returns the index of the
             // anonymous bdd var representing that state
@@ -300,6 +300,9 @@ namespace spot
                 old_to_new.emplace(st, new_st);
                 var_to_state.emplace(v, new_st);
 
+                if (sere_aut->state_is_accepting(st))
+                  acc_states.push_back(new_st);
+
                 vars &= bdd_ithvar(v);
               }
 
@@ -345,9 +348,22 @@ namespace spot
                   }
               }
 
+            for (unsigned st = 0; st < ns; ++st)
+              {
+                auto it = old_to_new.find(st);
+                assert(it != old_to_new.end());
+                unsigned new_st = it->second;
+
+                bdd comb = bddtrue;
+                comb &= oe_(new_st, acc_states);
+                comb &= oe_(rhs_init);
+                oe_.new_dests(new_st, comb);
+              }
+
             auto it = old_to_new.find(sere_aut->get_init_state_number());
             assert(it != old_to_new.end());
 
+            //aut_->merge_edges();
             return it->second;
           }