diff --git a/src/pymc_core/hardware/signal_utils.py b/src/pymc_core/hardware/signal_utils.py
index 65b57c0..d317001 100644
--- a/src/pymc_core/hardware/signal_utils.py
+++ b/src/pymc_core/hardware/signal_utils.py
@@ -2,8 +2,10 @@
 
 from __future__ import annotations
 
+from typing import Optional
 
-def snr_register_to_db(raw_value: int | None, *, bits: int = 8) -> float:
+
+def snr_register_to_db(raw_value: Optional[int], *, bits: int = 8) -> float:
     """Convert signed SX126x/SX127x SNR register (value * 4) into dB.
 
     Args:
diff --git a/src/pymc_core/hardware/sx1262_wrapper.py b/src/pymc_core/hardware/sx1262_wrapper.py
index c8d54e5..46f89b4 100644
--- a/src/pymc_core/hardware/sx1262_wrapper.py
+++ b/src/pymc_core/hardware/sx1262_wrapper.py
@@ -8,7 +8,7 @@
 import math
 import random
 import time
-from typing import Optional
+from typing import Optional, Union
 
 from .base import LoRaRadio
 from .gpio_manager import GPIOPinManager
@@ -1275,11 +1275,11 @@ def _get_thresholds_for_current_settings(self) -> tuple[int, int]:
 
     async def perform_cad(
         self,
-        det_peak: int | None = None,
-        det_min: int | None = None,
+        det_peak: Optional[int] = None,
+        det_min: Optional[int] = None,
         timeout: float = 1.0,
         calibration: bool = False,
-    ) -> bool | dict:
+    ) -> Union[bool, dict]:
         """
         Perform Channel Activity Detection (CAD).
         If calibration=True, uses provided thresholds and returns info.
diff --git a/src/pymc_core/protocol/packet.py b/src/pymc_core/protocol/packet.py
index f77fd9b..b405256 100644
--- a/src/pymc_core/protocol/packet.py
+++ b/src/pymc_core/protocol/packet.py
@@ -1,4 +1,4 @@
-from typing import ByteString
+from typing import ByteString, Optional
 
 from .constants import (
     MAX_PATH_SIZE,
@@ -366,12 +366,12 @@ def calculate_packet_hash(self) -> bytes:
             self.get_payload_type(), self.path_len, self.payload
         )
 
-    def get_packet_hash_hex(self, length: int | None = None) -> str:
+    def get_packet_hash_hex(self, length: Optional[int] = None) -> str:
         """
         Return upper-case hex string representation of this packet's hash.
 
         Args:
-            length (int | None, optional): Maximum length of the returned hex string.
+            length (Optional[int], optional): Maximum length of the returned hex string.
                 Defaults to None (full hash string).
 
         Returns:
diff --git a/src/pymc_core/protocol/packet_utils.py b/src/pymc_core/protocol/packet_utils.py
index f74b1a9..7164192 100644
--- a/src/pymc_core/protocol/packet_utils.py
+++ b/src/pymc_core/protocol/packet_utils.py
@@ -5,7 +5,7 @@
 
 import hashlib
 import struct
-from typing import Any, List, Union
+from typing import Any, List, Optional, Union
 
 from .constants import (
     MAX_HASH_SIZE,
@@ -223,7 +223,7 @@ def calculate_packet_hash_string(
         payload_type: int,
         path_len: int,
         payload: bytes,
-        length: int | None = None,
+        length: Optional[int] = None,
     ) -> str:
         """
         Return upper-case hex string representation of the packet hash.