diff --git a/CHERICC_Fat.bsv b/CHERICC_Fat.bsv
index f140fd2..0323769 100644
--- a/CHERICC_Fat.bsv
+++ b/CHERICC_Fat.bsv
@@ -830,6 +830,7 @@ instance CHERICap #(CapMem, 18, 64);
   function nullWithAddr = error("feature not implemented for this cap type");
   function almightyCap = error("feature not implemented for this cap type");
   function nullCap = error("feature not implemented for this cap type");
+  function validAsType = error("feature not implemented for this cap type");
 endinstance
 
 instance CHERICap #(CapReg, 18, 64);
@@ -854,6 +855,7 @@ instance CHERICap #(CapReg, 18, 64);
   function nullWithAddr = error("feature not implemented for this cap type");
   function almightyCap = defaultCapFat;
   function nullCap = null_cap;
+  function validAsType = error("feature not implemented for this cap type");
 endinstance
 
 instance CHERICap #(CapPipe, 18, 64);
@@ -978,6 +980,11 @@ instance CHERICap #(CapPipe, 18, 64);
 
   function nullCap = CapPipe { capFat: nullCap, tempFields: getTempFields(nullCap) };
 
+  function Bool validAsType (CapPipe dummy, Bit#(64) checkType);
+      UInt#(64) checkTypeUnsigned = unpack(checkType);
+      UInt#(64) otypeMaxUnsigned = unpack(zeroExtend(otype_max));
+      return checkTypeUnsigned <= otypeMaxUnsigned;
+  endfunction
 endinstance
 
 instance Cast#(CapMem, CapReg);
diff --git a/CHERICap.bsv b/CHERICap.bsv
index c156659..9ec5333 100644
--- a/CHERICap.bsv
+++ b/CHERICap.bsv
@@ -151,6 +151,9 @@ typeclass CHERICap#(type t, numeric type ot, numeric type n)
   // Return the null capability
   function t nullCap;
 
+  // Check if a type is valid
+  function Bool validAsType (t dummy, Bit#(n) checkType);
+
 endtypeclass
 
 function Fmt showCHERICap(t cap) provisos (CHERICap#(t, ot, n));