diff --git a/lib/mempool/mempool.js b/lib/mempool/mempool.js
index 25a48abb..f40c7837 100644
--- a/lib/mempool/mempool.js
+++ b/lib/mempool/mempool.js
@@ -1687,10 +1687,14 @@ Mempool.prototype.memUsage = function memUsage(tx) {
   var mem = 0;
   var i, j, input, output, coin, op;
 
-  mem += 264; // tx
+  mem += 264; // tx (note: probably more now due to hhash pointer)
   mem += 80; // _hash
+  mem += 88; // _hhash
   mem += 80; // _raw
 
+  if (tx._whash)
+    mem += 80; // _whash
+
   mem += 32; // input array
 
   for (i = 0; i < tx.inputs.length; i++) {