diff --git a/recipes/007_benchmarks_advanced.py b/recipes/007_benchmarks_advanced.py
index 9374fce..2eb36a5 100644
--- a/recipes/007_benchmarks_advanced.py
+++ b/recipes/007_benchmarks_advanced.py
@@ -77,7 +77,8 @@ def evaluate_constraints(self, params: dict[str, float]) -> tuple[float]:
         x = params["x"]
         c0 = x - 2
         if "y" not in params:
-            return [c0]
+            c1 = 0.0  # c1 <= 0, so c1 is satisfied in this case.
+            return c0, c1
         else:
             y = params["y"]
             c1 = x + y - 3