use Error

lib/server.js

@@ -1121,7 +1121,7 @@ WalletService.prototype.getTxHistory = function(opts, cb) {
       },
       function(next) {
         bc.getTransactions(addressStrs, null, null, function(err, txs) {
-          if (err) return next('Could not fetch transactions: ' + err);
+          if (err) return next(new Error('Could not fetch transactions: ' + err));
 
           next(null, self._normalizeTxHistory(txs));
         });
@@ -1179,7 +1179,7 @@ WalletService.prototype.scan = function(opts, cb) {
         if (err) return next(err);
         allAddresses.push(addresses);
         checkActivity(_.pluck(addresses, 'address'), function(err, thereIsActivity) {
-          if (err) return next('Could not fetch TX activity:' + err);
+          if (err) return next(new Error('Could not fetch TX activity:' + err));
           activity = thereIsActivity;
           next();
         });