4 files changed, 4 insertions, 4 deletions
diff --git a/Acl/Domain/UserSecurityIdentity.php b/Acl/Domain/UserSecurityIdentity.php
index 3bf277f..ea17c63 100644
--- a/Acl/Domain/UserSecurityIdentity.php
+++ b/Acl/Domain/UserSecurityIdentity.php
@@ -36,7 +36,7 @@ final class UserSecurityIdentity implements SecurityIdentityInterface
      */
     public function __construct($username, $class)
     {
-        if (empty($username)) {
+        if ('' === $username || null === $username) {
             throw new \InvalidArgumentException('$username must not be empty.');
         }
         if (empty($class)) {
diff --git a/Core/Authentication/Provider/UserAuthenticationProvider.php b/Core/Authentication/Provider/UserAuthenticationProvider.php
index ded53e4..2674088 100644
--- a/Core/Authentication/Provider/UserAuthenticationProvider.php
+++ b/Core/Authentication/Provider/UserAuthenticationProvider.php
@@ -62,7 +62,7 @@ abstract class UserAuthenticationProvider implements AuthenticationProviderInter
         }
 
         $username = $token->getUsername();
-        if (empty($username)) {
+        if ('' === $username || null === $username) {
             $username = 'NONE_PROVIDED';
         }
 
diff --git a/Core/Authentication/RememberMe/PersistentToken.php b/Core/Authentication/RememberMe/PersistentToken.php
index 92fcb4f..d85572d 100644
--- a/Core/Authentication/RememberMe/PersistentToken.php
+++ b/Core/Authentication/RememberMe/PersistentToken.php
@@ -40,7 +40,7 @@ final class PersistentToken implements PersistentTokenInterface
         if (empty($class)) {
             throw new \InvalidArgumentException('$class must not be empty.');
         }
-        if (empty($username)) {
+        if ('' === $username || null === $username) {
             throw new \InvalidArgumentException('$username must not be empty.');
         }
         if (empty($series)) {
diff --git a/Core/User/User.php b/Core/User/User.php
index ea2c6a4..86f1acd 100644
--- a/Core/User/User.php
+++ b/Core/User/User.php
@@ -30,7 +30,7 @@ final class User implements AdvancedUserInterface
 
     public function __construct($username, $password, array $roles = array(), $enabled = true, $userNonExpired = true, $credentialsNonExpired = true, $userNonLocked = true)
     {
-        if (empty($username)) {
+        if ('' === $username || null === $username) {
             throw new \InvalidArgumentException('The username cannot be empty.');
         }