diff --git a/lib/TransactionDb.js b/lib/TransactionDb.js
index 4f1dbe4..06a558b 100644
--- a/lib/TransactionDb.js
+++ b/lib/TransactionDb.js
@@ -103,8 +103,15 @@ function spec(b) {
             assert(typeof j !== 'undefined','Spent could not be stored: tx ' + txid +
                    'spend in TX:' + k[2] + ',' + k[3]+ ' j:' + j);
 
-            ret[j].spendTxId  = v[0];
-            ret[j].spendIndex = parseInt(v[1]);
+/// TODO Handle multiple addresses here!
+            if (ret[j].spendTxId) {
+              // double spend!
+              assert(0);
+            }
+            else  {
+              ret[j].spendTxId  = v[0];
+              ret[j].spendIndex = parseInt(v[1]);
+            }
           })
           .on('error', function (err) {
             return cb(err);