diff --git a/windows/winobject/process.py b/windows/winobject/process.py
index 24075d8..830531b 100644
--- a/windows/winobject/process.py
+++ b/windows/winobject/process.py
@@ -925,7 +925,7 @@ class WinThread(Thread):
         # - Want the TEB of a 64b process
         # - Want the TEB64 of a Wowprocess
         # It's the same code for both
-        if windows.current_process._is_x86_on_arm64 and not self.bitness == 32:
+        if windows.current_process._is_x86_on_arm64 and not self.owner.bitness == 32:
             raise NotImplementedError("Crossing heaven gate x86 -> arm64 not implemented")
 
         if windows.current_process.is_wow_64: