diff --git a/spot/twaalgos/cleanacc.cc b/spot/twaalgos/cleanacc.cc
index e1cfed932..913c2f10b 100644
--- a/spot/twaalgos/cleanacc.cc
+++ b/spot/twaalgos/cleanacc.cc
@@ -124,7 +124,7 @@ namespace spot
           while (rbegin > rend);
           if (rbegin <= rend)
             return res;
-          // Fin(i) & Inf(i) = f;
+          // Fin(i) & Inf(i) = f;             (also done by unit-fin)
           if (rbegin[-1].mark & seen_fin)
             return std::move(falsecode);
           for (auto m: seen_fin.sets())
@@ -192,6 +192,8 @@ namespace spot
         return aut;
 
       // complement[i] holds sets that appear when set #i does not.
+      // (This is not a strict complement, i.e., the sets in
+      // complement[i] are allowed to occur at the same time as i.)
       unsigned num_sets = acc.num_sets();
       std::vector<acc_cond::mark_t> complement(num_sets);
 
@@ -214,12 +216,8 @@ namespace spot
         {
           prev_acc = tacc;
           for (unsigned m: used_in_cond.sets())
-            {
-              if (tacc.has(m))
-                complement[m] -= tacc;
-              else
-                complement[m] &= tacc;
-            }
+            if (!tacc.has(m))
+              complement[m] &= tacc;
         };
       if (b != e)
         {
diff --git a/tests/python/toparity.py b/tests/python/toparity.py
index f8ce7dc1a..a7b034f21 100644
--- a/tests/python/toparity.py
+++ b/tests/python/toparity.py
@@ -220,6 +220,21 @@ State: 1
 [!0&!1] 1 {0 3}
 --END--"""), [7, 5, 3, 6, 5, 5, 3])
 
+test(spot.automaton("""HOA: v1
+States: 2
+Start: 0
+AP: 2 "p0" "p1"
+Acceptance: 5 ((Fin(1)|Fin(3)|Fin(4)) | Inf(2) | Inf(0))
+               & (Inf(0) | Inf(1)) & (Inf(2) | Inf(1))
+properties: trans-labels explicit-labels trans-acc deterministic
+--BODY--
+State: 0
+[0&1] 0 {1 3}
+[!0&1] 1 {0}
+State: 1
+[0&1] 1 {2 3 4}
+[!0&!1] 0 {1 2}
+--END--"""), [9, 3, 2, 3, 3, 3, 2])
 
 for i,f in enumerate(spot.randltl(10, 400)):
     test(spot.translate(f, "det", "G"), full=(i<100))