diff --git a/global-functions.rsc b/global-functions.rsc
index 22579f90..e6638154 100644
--- a/global-functions.rsc
+++ b/global-functions.rsc
@@ -1014,31 +1014,9 @@
 
 # return an IPv6 netmask for CIDR
 :set NetMask6 do={
-  :local CIDR [ :tostr $1 ];
+  :local CIDR [ :tonum $1 ];
 
-  :global IfThenElse;
-  :global MAX;
-  :global MIN;
-
-  :global NetMask6Cache;
-
-  :if ([ :typeof ($NetMask6Cache->$CIDR) ] = "ip6") do={
-    :return ($NetMask6Cache->$CIDR);
-  }
-
-  :if ([ :typeof $NetMask6Cache ] = "nothing") do={
-    :set NetMask6Cache ({});
-  }
-
-  :local Mask "";
-  :for I from=0 to=7 do={
-    :set Mask ($Mask . \
-      [ :convert from=num to=hex (0xffff - (0xffff >> [ :tonum [ $MIN [ $MAX ($CIDR - (16 * $I)) 0 ] 16 ] ])) ] . \
-      [ $IfThenElse ($I < 7) ":" ]);
-  }
-  :set Mask [ :toip6 $Mask ];
-  :set ($NetMask6Cache->$CIDR) $Mask;
-  :return $Mask;
+  :return (((~::) << (128 - $CIDR)) & (~::));
 }
 
 # prepare NotificationFunctions array