diff --git a/Tests/Succeed/Test186.ML b/Tests/Succeed/Test186.ML
index 72106c90..a0bb2a70 100644
--- a/Tests/Succeed/Test186.ML
+++ b/Tests/Succeed/Test186.ML
@@ -1,38 +1,40 @@
 (* IPv6 test - Test078 converted to IPv6 *)
+(* IPv6 may not be configured but it's not clear where the error will occur. *)
 val x = INet6Sock.TCP.socket(): Socket.passive INet6Sock.stream_sock
-and y = INet6Sock.TCP.socket(): Socket.active INet6Sock.stream_sock;
+            handle OS.SysErr _ => raise NotApplicable;
+
+val y = INet6Sock.TCP.socket(): Socket.active INet6Sock.stream_sock;
 
-(* IPv6 may not be configured but it's not clear where the error will occur. *)
 val me = case Net6HostDB.getByName "localhost" of SOME me => me | NONE => raise NotApplicable;
 
 val localhost = Net6HostDB.addr me;
 
 Socket.bind(x, INet6Sock.toAddr(localhost, 0))
     handle exn as OS.SysErr(_, SOME e) =>
       (case OS.syserror "EADDRNOTAVAIL" of
         SOME f => if e = f then raise NotApplicable else raise exn | NONE => raise exn);
 
 Socket.listen(x, 5);
 let
 val (_, port) = INet6Sock.fromAddr(Socket.Ctl.getSockName x)
 in
 Socket.connect(y, INet6Sock.toAddr(localhost, port))
 end;
 val (cnct, _) = Socket.accept x;
 
 (* Send the data. Use a separate thread so there's no possibility of blocking. *)
 let
     fun sendData() =
         (Socket.sendVec(y, Word8VectorSlice.full(Byte.stringToBytes "A test")); ())
 in
     Thread.Thread.fork(sendData, [])
 end;
 
 if Byte.bytesToString(Socket.recvVec(cnct, 6)) <> "A test"
 then raise Fail "failed"
 else ();
 
 Socket.close cnct;
 Socket.close x;
 Socket.close y;