From b15703f4316c0a670fbb71644e8e54133da31977 Mon Sep 17 00:00:00 2001
From: Stavros Efthymiou <35475381+stavros11@users.noreply.github.com>
Date: Mon, 16 Oct 2023 14:24:55 +0400
Subject: [PATCH] Correct check

---
 src/qibo/parallel.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/qibo/parallel.py b/src/qibo/parallel.py
index ab69c3fdfd..b79c4e348d 100644
--- a/src/qibo/parallel.py
+++ b/src/qibo/parallel.py
@@ -92,7 +92,11 @@ def parallel_circuits_execution(
     if not isinstance(circuits, Iterable):  # pragma: no cover
         raise_error(TypeError, "circuits must be iterable.")
 
-    if isinstance(states, (list, tuple)) and len(states) != len(circuits):
+    if (
+        isinstance(states, (list, tuple))
+        and isinstance(circuits, (list, tuple))
+        and len(states) != len(circuits)
+    ):
         raise_error(ValueError, "states must have the same length as circuits.")
     elif states is not None and not isinstance(states, Iterable):
         raise_error(TypeError, "states must be iterable.")