diff -r 8c5eedb6c983 -r c51e1cef1eae src/Pure/General/socket_io.ML
--- a/src/Pure/General/socket_io.ML	Tue Jun 21 16:03:00 2022 +0200
+++ b/src/Pure/General/socket_io.ML	Tue Jun 21 22:17:11 2022 +0200
@@ -96,6 +96,6 @@
 
 fun with_streams' f socket_name password =
   with_streams (fn streams =>
-    (Byte_Message.write_line (#2 streams) password; f streams)) socket_name;
+    (Byte_Message.write_line (#2 streams) (Bytes.string password); f streams)) socket_name;
 
 end;