Index: pypy/module/posix/interp_posix.py
===================================================================
--- pypy/module/posix/interp_posix.py	(revision 46516:af690ea765e2)
+++ pypy/module/posix/interp_posix.py	(revision 46516+:af690ea765e2+)
@@ -739,7 +739,7 @@
         if len(args_w) < 1:
             w_msg = space.wrap("execv() must have at least one argument")
             raise OperationError(space.w_ValueError, w_msg)
-        args = [space.str_w(w_arg) for w_arg in args_w]
+        args = [FileEncoder(w_arg) for w_arg in args_w]
     except OperationError, e:
         if not e.match(space, space.w_TypeError):
             raise
@@ -760,7 +760,7 @@
         args: iterable of arguments
         env: dictionary of strings mapping to strings
     """
-    args = [space.str_w(w_arg) for w_arg in space.unpackiterable(w_args)]
+    args = [FileEncoder(w_arg) for w_arg in space.unpackiterable(w_args)]
     env = {}
     w_keys = space.call_method(w_env, 'keys')
     for w_key in space.unpackiterable(w_keys):
@@ -773,7 +773,7 @@

 @unwrap_spec(mode=int, path=str)
 def spawnv(space, mode, path, w_args):
-    args = [space.str_w(w_arg) for w_arg in space.unpackiterable(w_args)]
+    args = [FileEncoder(w_arg) for w_arg in space.unpackiterable(w_args)]
     try:
         ret = os.spawnv(mode, path, args)
     except OSError, e: