diff --git a/CHERICC_Fat.bsv b/CHERICC_Fat.bsv
index cbcdab5..01f439b 100644
--- a/CHERICC_Fat.bsv
+++ b/CHERICC_Fat.bsv
@@ -1224,9 +1224,9 @@ instance Cast#(function CapReg f0(t x), function CapPipe f1(t y));
   endfunction
 endinstance
 
-instance Cast#(function CapPipe f0(t y), function Bit#(64) f1(t x));
+instance Cast#(function CapPipe f0(t y), function Bit#(CapAddressW) f1(t x));
   function cast(f0);
-      function Bit#(64) f1(t arg) = getAddr(f0(arg));
+      function Bit#(CapAddressW) f1(t arg) = getAddr(f0(arg));
       return f1;
   endfunction
 endinstance