diff --git a/lib/wallet/txdb.js b/lib/wallet/txdb.js
index 441d34cd..ba98acc5 100644
--- a/lib/wallet/txdb.js
+++ b/lib/wallet/txdb.js
@@ -1919,6 +1919,7 @@ TXDB.prototype.getAccountBalance = co(function* getBalance(account) {
 
 TXDB.prototype.zap = co(function* zap(account, age) {
   var hashes = [];
+  var now = utils.now();
   var i, txs, tx, hash;
 
   if (!utils.isUInt32(age))
@@ -1926,7 +1927,7 @@ TXDB.prototype.zap = co(function* zap(account, age) {
 
   txs = yield this.getRange(account, {
     start: 0,
-    end: utils.now() - age
+    end: now - age
   });
 
   for (i = 0; i < txs.length; i++) {
@@ -1936,6 +1937,8 @@ TXDB.prototype.zap = co(function* zap(account, age) {
     if (tx.ts !== 0)
       continue;
 
+    assert(now - tx.ps >= age);
+
     this.wallet.start();
 
     this.logger.debug('Zapping TX: %s (%s)',