diff --git a/tools/computer_use/cua_backend.py b/tools/computer_use/cua_backend.py
index cbc4a17de4c2..6d2f6b5c6ff5 100644
--- a/tools/computer_use/cua_backend.py
+++ b/tools/computer_use/cua_backend.py
@@ -199,7 +199,7 @@ def _cua_no_overlay() -> bool:
     if not os.environ.get("DISPLAY"):
         return True
     try:
-        with open("/proc/version") as f:
+        with open("/proc/version", encoding="utf-8") as f:
             if "microsoft" in f.read().lower():
                 return True
     except Exception: