diff --git a/src/qibo/gates/abstract.py b/src/qibo/gates/abstract.py
index 023aaac48f..b829392995 100644
--- a/src/qibo/gates/abstract.py
+++ b/src/qibo/gates/abstract.py
@@ -123,17 +123,17 @@ def to_json(self):
         return json.dumps(self.raw)
 
     @property
-    def target_qubits(self) -> Tuple[int]:
+    def target_qubits(self) -> Tuple[int, ...]:
         """Tuple with ids of target qubits."""
         return self._target_qubits
 
     @property
-    def control_qubits(self) -> Tuple[int]:
+    def control_qubits(self) -> Tuple[int, ...]:
         """Tuple with ids of control qubits sorted in increasing order."""
         return tuple(sorted(self._control_qubits))
 
     @property
-    def qubits(self) -> Tuple[int]:
+    def qubits(self) -> Tuple[int, ...]:
         """Tuple with ids of all qubits (control and target) that the gate acts."""
         return self.control_qubits + self.target_qubits
 
diff --git a/src/qibo/gates/measurements.py b/src/qibo/gates/measurements.py
index 50b4c29e78..34e1ca4f1a 100644
--- a/src/qibo/gates/measurements.py
+++ b/src/qibo/gates/measurements.py
@@ -103,7 +103,9 @@ def __init__(
                 self.basis.append(gate)
 
     @staticmethod
-    def _get_bitflip_tuple(qubits: Tuple[int], probs: "ProbsType") -> Tuple[float]:
+    def _get_bitflip_tuple(
+        qubits: Tuple[int, ...], probs: "ProbsType"
+    ) -> Tuple[float, ...]:
         if isinstance(probs, float):
             if probs < 0 or probs > 1:  # pragma: no cover
                 raise_error(ValueError, f"Invalid bitflip probability {probs}.")