diff --git a/tests/clingexplaid/test_muc.py b/tests/clingexplaid/test_muc.py
index 9467304..1c69241 100644
--- a/tests/clingexplaid/test_muc.py
+++ b/tests/clingexplaid/test_muc.py
@@ -154,7 +154,7 @@ def test_core_computer_shrink_large_instance_random(self) -> None:
         ctl = clingo.Control()
 
         n_assumptions = 1000
-        random_core = random.choices(range(n_assumptions), k=10)
+        random_core = random.choices(range(1, n_assumptions), k=10)
         program = f"""
             a(1..{n_assumptions}).
             :- {', '.join([f"a({i})" for i in random_core])}.