diff --git a/lib/mempool/mempool.js b/lib/mempool/mempool.js
index 0e0cd0c6..17567770 100644
--- a/lib/mempool/mempool.js
+++ b/lib/mempool/mempool.js
@@ -666,10 +666,10 @@ Mempool.prototype.addTX = co(function* addTX(tx) {
  */
 
 Mempool.prototype._addTX = co(function* _addTX(tx) {
-  var result;
+  var missing;
 
   try {
-    result = yield this.insertTX(tx);
+    missing = yield this.insertTX(tx);
   } catch (err) {
     if (err.type === 'VerifyError') {
       if (!tx.hasWitness() && !err.malleated)
@@ -682,6 +682,8 @@ Mempool.prototype._addTX = co(function* _addTX(tx) {
     yield this.cache.flush();
     this.lastUpdate = util.now();
   }
+
+  return missing;
 });
 
 /**