diff --git a/src/qibotn/mps_contraction_helper.py b/src/qibotn/mps_contraction_helper.py
index 9c71200..ee8e4e4 100644
--- a/src/qibotn/mps_contraction_helper.py
+++ b/src/qibotn/mps_contraction_helper.py
@@ -105,7 +105,7 @@ class MPSContractionHelper:
         interleaved_inputs = []
         extra_mode = 3 * self.num_qubits + 2
         operator_modes = [None] * len(qubits) + [self.bra_modes[q][1] for q in qubits]
-        qubits = [q for q in qubits]
+        qubits = list(qubits)
         for i, o in enumerate(mps_tensors):
             interleaved_inputs.extend([o, self.bra_modes[i]])
             k_modes = self.ket_modes[i]