diff --git a/src/hardware_service.pyx b/src/hardware_service.pyx
index a5d658f..ba001aa 100644
--- a/src/hardware_service.pyx
+++ b/src/hardware_service.pyx
@@ -1,11 +1,12 @@
 import os
 import platform
 import subprocess
+from typing import Optional
 
 import psutil
 cimport constants
 
-cdef str _CACHED_HW_INFO = None
+cdef Optional[str] _CACHED_HW_INFO = None
 
 
 def _get_cpu():