diff --git a/src/Symfony/Bridge/Doctrine/Validator/Constraints/UniqueEntityValidator.php b/src/Symfony/Bridge/Doctrine/Validator/Constraints/UniqueEntityValidator.php
index 51181b0714..b0d9534a0e 100644
--- a/src/Symfony/Bridge/Doctrine/Validator/Constraints/UniqueEntityValidator.php
+++ b/src/Symfony/Bridge/Doctrine/Validator/Constraints/UniqueEntityValidator.php
@@ -62,6 +62,10 @@ class UniqueEntityValidator extends ConstraintValidator
             throw new ConstraintDefinitionException('At least one field has to be specified.');
         }
 
+        if (null === $entity) {
+            return;
+        }
+
         if ($constraint->em) {
             $em = $this->registry->getManager($constraint->em);
 
diff --git a/src/Symfony/Component/Security/Core/Validator/Constraints/UserPasswordValidator.php b/src/Symfony/Component/Security/Core/Validator/Constraints/UserPasswordValidator.php
index 2dc7fee499..5f4c146cab 100644
--- a/src/Symfony/Component/Security/Core/Validator/Constraints/UserPasswordValidator.php
+++ b/src/Symfony/Component/Security/Core/Validator/Constraints/UserPasswordValidator.php
@@ -39,6 +39,10 @@ class UserPasswordValidator extends ConstraintValidator
             throw new UnexpectedTypeException($constraint, __NAMESPACE__.'\UserPassword');
         }
 
+        if (null === $password || '' === $password) {
+            return;
+        }
+
         $user = $this->tokenStorage->getToken()->getUser();
 
         if (!$user instanceof UserInterface) {
diff --git a/src/Symfony/Component/Validator/Constraints/UrlValidator.php b/src/Symfony/Component/Validator/Constraints/UrlValidator.php
index 5cb126d8fe..26246fe6d2 100644
--- a/src/Symfony/Component/Validator/Constraints/UrlValidator.php
+++ b/src/Symfony/Component/Validator/Constraints/UrlValidator.php
@@ -48,7 +48,7 @@ class UrlValidator extends ConstraintValidator
             throw new UnexpectedTypeException($constraint, __NAMESPACE__.'\Url');
         }
 
-        if (null === $value) {
+        if (null === $value || '' === $value) {
             return;
         }