diff --git a/tests/performance/compare_algo/nqueens/nqueens_test_prolog_plain.sh b/tests/performance/compare_algo/nqueens/nqueens_test_prolog_plain.sh
index 58307131490..3f204fad136 100755
--- a/tests/performance/compare_algo/nqueens/nqueens_test_prolog_plain.sh
+++ b/tests/performance/compare_algo/nqueens/nqueens_test_prolog_plain.sh
@@ -43,9 +43,9 @@ nqueens(N, Solution) :-
 % Start the benchmark
 benchmark(N) :-
     statistics(walltime, [_ | [_]]),
-    nqueens(N, Solution),
+    findall(S, nqueens(N, S), Solutions),
+    length(Solutions, Length),
     statistics(walltime, [_ | [Elapsed]]),
-    length(Solution, Length),
     format("N=~w: ~w solutions found in ~w ms~n", [N, Length, Elapsed]).
 EOF