diff -r 1eca7abaa015 -r f34a451f7b5b src/Pure/General/socket_io.ML
--- a/src/Pure/General/socket_io.ML	Tue Sep 26 13:34:04 2023 +0200
+++ b/src/Pure/General/socket_io.ML	Tue Sep 26 13:37:08 2023 +0200
@@ -92,7 +92,9 @@
     let
       val streams = open_streams socket_name;
       val result = Exn.capture (run f) streams;
-    in BinIO.closeIn (#1 streams); BinIO.closeOut (#2 streams); Exn.release result end);
+      val _ = BinIO.closeIn (#1 streams);
+      val _ = BinIO.closeOut (#2 streams);
+    in Exn.release result end);
 
 fun with_streams' f socket_name password =
   with_streams (fn streams =>