diff --git a/src/calibre/startup.py b/src/calibre/startup.py
index bda31e1a3b..c89d95d4b4 100644
--- a/src/calibre/startup.py
+++ b/src/calibre/startup.py
@@ -107,7 +107,8 @@ def initialize_calibre():
 
     def wrapped_orig_spawn_fds(args, passfds):
         # as of python 3.11 util.spawnv_passfds expects bytes args
-        args = [x.encode('utf-8') if isinstance(x, str) else x for x in args]
+        if sys.version_info >= (3, 11):
+            args = [x.encode('utf-8') if isinstance(x, str) else x for x in args]
         return orig_spawn_passfds(args[0], args, passfds)
 
     def spawnv_passfds(path, args, passfds):