diff --git a/spot/tl/apcollect.cc b/spot/tl/apcollect.cc
index 61a570f3d..72e4335f9 100644
--- a/spot/tl/apcollect.cc
+++ b/spot/tl/apcollect.cc
@@ -411,9 +411,9 @@ namespace spot
                       continue;
                     SPOT_ASSUME(lit != nullptr);
                     if (lit.is(spot::op::Not))
-                      add_to_mapping(lit[0], repr_is_input, not_repr);
+                      add_to_mapping(lit[0], false, not_repr);
                     else
-                      add_to_mapping(lit, repr_is_input, repr);
+                      add_to_mapping(lit, false, repr);
                     rm_has_new_terms = true;
                   }
               }
diff --git a/tests/core/ltlsynt.test b/tests/core/ltlsynt.test
index 537872c23..7165f00c5 100644
--- a/tests/core/ltlsynt.test
+++ b/tests/core/ltlsynt.test
@@ -1109,4 +1109,14 @@ diff out expected
 
 f1="((G ((p0) <-> (! (p1)))) && (((((F ((b) && (G (F (a))))) ||\
   (F ((c) && (G (F (! (a))))))) && (F (b))) && (F (c))) <-> (G (F (p0)))))"
-ltlsynt -f "$f1" --outs="p1, p0" --aiger > /dev/null
\ No newline at end of file
+ltlsynt -f "$f1" --outs="p1, p0" --aiger > /dev/null
+
+# issue #557
+ltlsynt  -f 'G(in1 <-> out0) & G(in0 <-> out1)' --ins=in1,in0 --verb 2>err >out
+grep := err > err2
+cat >err2.ex <<EOF
+  out0 := in1
+  out1 := in0
+EOF
+diff err2 err2.ex
+grep -F '[!0&!1&!2&!3 | !0&!1&2&3 | 0&1&!2&!3 | 0&1&2&3] 0' out