diff --git a/src/qiskit_qec/operators/pauli.py b/src/qiskit_qec/operators/pauli.py
index e0a01889..46aac06d 100644
--- a/src/qiskit_qec/operators/pauli.py
+++ b/src/qiskit_qec/operators/pauli.py
@@ -521,11 +521,11 @@ def to_instruction(self):
             gate = {"I": IGate(), "X": XGate(), "Y": YGate(), "Z": ZGate()}[pauli]
         else:
             gate = PauliGate(pauli)
-        if not phase_exp[0]:
+        if not phase_exp:
             return gate
         # Add global phase
         circuit = QuantumCircuit(self.num_qubits, name=str(self))
-        circuit.global_phase = -phase_exp[0] * pi / 2
+        circuit.global_phase = -phase_exp * pi / 2
         circuit.append(gate, range(self.num_qubits))
         return circuit.to_instruction()
 
diff --git a/tox.ini b/tox.ini
index 958c0931..39a13053 100644
--- a/tox.ini
+++ b/tox.ini
@@ -10,10 +10,12 @@ setenv =
   VIRTUAL_ENV={envdir}
   LANGUAGE=en_US
   LC_ALL=en_US.utf-8
+  JUPYTER_PLATFORM_DIRS=1
 deps = -r requirements.txt
        -r requirements-dev.txt
 commands =
   pip check
+  jupyter --paths
   python -m unittest discover -s test/ -p '*test*.py' -v
 
 [testenv:lint]