diff --git a/otherlibs/threads/unix.ml b/otherlibs/threads/unix.ml
index 80ca75b6b..fc60121b7 100644
--- a/otherlibs/threads/unix.ml
+++ b/otherlibs/threads/unix.ml
@@ -844,7 +844,7 @@ let establish_server server_fun sockaddr =
     socket domain SOCK_STREAM 0 in
   setsockopt sock SO_REUSEADDR true;
   bind sock sockaddr;
-  listen sock 3;
+  listen sock 5;
   while true do
     let (s, caller) = accept sock in
     (* The "double fork" trick, the process which calls server_fun will not
@@ -854,8 +854,11 @@ let establish_server server_fun sockaddr =
             let inchan = in_channel_of_descr s in
             let outchan = out_channel_of_descr s in
             server_fun inchan outchan;
-            close_in inchan;
-            close_out outchan
+            close_out outchan;
+            (* The file descriptor was already closed by close_out.
+               close_in inchan;
+            *)
+            exit 0
     | id -> close s; ignore(waitpid [] id) (* Reclaim the son *)
   done