diff --git a/basis/Weak.sml b/basis/Weak.580.sml
similarity index 100%
copy from basis/Weak.sml
copy to basis/Weak.580.sml
diff --git a/basis/Weak.sml b/basis/Weak.sml
index aee1c736..233328ed 100644
--- a/basis/Weak.sml
+++ b/basis/Weak.sml
@@ -1,61 +1,61 @@
 (*
     Title:      Weak references
     Author:     David Matthews
-    Copyright   David Matthews 2008, 2015-16
+    Copyright   David Matthews 2008, 2015-16, 2019
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Lesser General Public
     License version 2.1 as published by the Free Software Foundation.
     
     This library is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Lesser General Public License for more details.
     
     You should have received a copy of the GNU Lesser General Public
     License along with this library; if not, write to the Free Software
     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *)
 
 (* A weak reference or array contains option values.  The SOME variant of
    the option must contain a reference.  This restriction is imposed because
    they require pointer equality.  A weak reference or array behaves just like
    a normal ref or array with one difference.  The garbage collector may set
    a weak ref or the field of weak array to NONE if it currently contains
    SOME r but r is not reachable other than through weak references.  The
    one proviso is that if r is contained in the executable it is always
    reachable.
 *)
 
 signature WEAK =
 sig
     val weak: 'a ref option -> 'a ref option ref
     val weakArray: int * 'a ref option -> 'a ref option array
     val weakLock: Thread.Mutex.mutex
     and weakSignal: Thread.ConditionVar.conditionVar
     val touch : 'a ref -> unit
 end;
 
 structure Weak: WEAK =
 struct
     fun weak (v: 'a ref option): 'a ref option ref = RunCall.allocateWordMemory(0w1, 0wx60, v)
     
     fun weakArray(n: int, v: 'a ref option): 'a ref option array =
     let
         val () = if n < 0 orelse n >= Array.maxLen then raise Size else ()
         val arr = RunCall.allocateWordMemory(Word.fromInt n, 0wx60, v)
     in
         arr
     end
 
     val weakLock = Thread.Mutex.mutex()
     and weakSignal = Thread.ConditionVar.conditionVar()
 
     (* touch is considered by the compiler as an access to the ref but doesn't
        actually do anything with it.  The idea is that it ensures that when a ref
        is used as a token that this will access the ref and avoid the weak
        reference becoming set to NONE.  It's primarily there for long-term
        security in the event that the compiler is sufficiently clever to
        work out that something is no longer referenced. *)
-    fun touch v = v := !v
+    val touch: 'a ref -> unit = RunCall.touch
 end;