diff --git a/lib/validations.js b/lib/validations.js
index 9cd368f9..6998f328 100644
--- a/lib/validations.js
+++ b/lib/validations.js
@@ -328,7 +328,9 @@ function validateCustom(attr, conf, err, done) {
  * Uniqueness validator
  */
 function validateUniqueness(attr, conf, err, done) {
-  if (blank(this[attr])) return done();
+  if (blank(this[attr])) {
+    return process.nextTick(done);
+  }
   var cond = {where: {}};
   cond.where[attr] = this[attr];