diff --git a/spot/twaalgos/mealy_machine.cc b/spot/twaalgos/mealy_machine.cc
index ac8107247..aa7821213 100644
--- a/spot/twaalgos/mealy_machine.cc
+++ b/spot/twaalgos/mealy_machine.cc
@@ -3725,13 +3725,12 @@ namespace spot
     assert(is_split_mealy(left));
     assert(is_split_mealy(right));
 
-    auto& spl = get_state_players(left);
-    auto& spr = get_state_players(right);
-
     const unsigned initl = left->get_init_state_number();
     const unsigned initr = right->get_init_state_number();
 
+    auto& spr = get_state_players(right);
 #ifndef NDEBUG
+    auto& spl = get_state_players(left);
     // todo
     auto check_out = [](const const_twa_graph_ptr& aut,
                         const auto& sp)
diff --git a/spot/twaalgos/synthesis.cc b/spot/twaalgos/synthesis.cc
index 08cfcad30..2143408b1 100644
--- a/spot/twaalgos/synthesis.cc
+++ b/spot/twaalgos/synthesis.cc
@@ -150,6 +150,7 @@ namespace{
 
     assert((sp[arena->get_init_state_number()] == false)
            && "Env needs to have first turn!");
+    (void)sp;
 
     assert(std::none_of(arena->edges().begin(), arena->edges().end(),
            [&sp](const auto& e)