diff --git a/lib/services/db/sync.js b/lib/services/db/sync.js
index e668393e..65ea54bb 100644
--- a/lib/services/db/sync.js
+++ b/lib/services/db/sync.js
@@ -261,11 +261,23 @@ ProcessSerial.prototype._transform = function(block, enc, callback) {
 
   async.whilst(
     function() {
-      return self.db.concurrentTip.__height < block.__height;
+      return self.db.concurrentTip.__height < block.__height || self.db.tip.__height < block.__height - 1;
     },
     function(next) {
+      var nextCalled = false;
       // wait until concurrent handler is ahead of us
-      setTimeout(next, 10);
+      self.db.once('addblock', function() {
+        if(!nextCalled) {
+          next();
+        }
+        nextCalled = true;
+      });
+      self.db.once('concurrentaddblock', function() {
+        if(!nextCalled) {
+          next();
+        }
+        nextCalled = true;
+      });
     },
     function() {
       self.db.getSerialBlockOperations(block, true, function(err, operations) {
@@ -361,6 +373,7 @@ WriteStream.prototype._write = function(obj, enc, callback) {
 
     if(obj.tip) {
       self.db.tip = obj.tip;
+      self.db.emit('addblock');
       if(self.db.tip.__height % 100 === 0) {
         console.log('Tip:', self.db.tip.__height);
       }
@@ -368,6 +381,7 @@ WriteStream.prototype._write = function(obj, enc, callback) {
 
     if(obj.concurrentTip) {
       self.db.concurrentTip = obj.concurrentTip;
+      self.db.emit('concurrentaddblock');
       if(self.db.concurrentTip.__height - self.lastConcurrentOutputHeight >= 100) {
         console.log('Concurrent tip:', self.db.concurrentTip.__height);
         self.lastConcurrentOutputHeight = self.db.concurrentTip.__height;