diff --git a/application/controllers/AuthenticationController.php b/application/controllers/AuthenticationController.php
index da687e36c..bf6f0db39 100644
--- a/application/controllers/AuthenticationController.php
+++ b/application/controllers/AuthenticationController.php
@@ -1,5 +1,4 @@
 <?php
-// @codingStandardsIgnoreStart
 // {{{ICINGA_LICENSE_HEADER}}}
 /**
  * This file is part of Icinga Web 2.
@@ -61,19 +60,22 @@ class AuthenticationController extends ActionController
         $this->view->form = new LoginForm();
         $this->view->form->setRequest($this->_request);
         $this->view->title = 'Icinga Web Login';
+
         try {
             $redirectUrl = Url::fromPath($this->_request->getParam('redirect', 'dashboard'));
+
             if ($this->_request->isXmlHttpRequest()) {
                 $redirectUrl->setParam('_render', 'layout');
             }
+
             $auth = AuthManager::getInstance();
             if ($auth->isAuthenticated()) {
                 $this->redirectNow($redirectUrl);
             }
+
             if ($this->view->form->isSubmittedAndValid()) {
-                $user = new User(
-                    $this->view->form->getValue('username')
-                );
+                $user = new User($this->view->form->getValue('username'));
+
                 try {
                     $config = Config::app('authentication');
                 } catch (NotReadableError $e) {
@@ -85,37 +87,33 @@ class AuthenticationController extends ActionController
                         . ' up. Please contact your Icinga Web administrator'
                     );
                 }
-                $backendsWithError = 0;
+
                 // TODO(el): Currently the user is only notified about authentication backend problems when all backends
                 // have errors. It may be the case that the authentication backend which provides the user has errors
                 // but other authentication backends work. In that scenario the user is presented an error message
                 // saying "Incorrect username or password". We must inform the user that not all authentication methods
                 // are available.
                 $backendsTried = 0;
+                $backendsWithError = 0;
                 $chain = new AuthChain($config);
                 foreach ($chain as $backend) {
-                    ++$backendsTried;
-                    try {
-                        if ($backend->authenticate($user, $this->view->form->getValue('password'))) {
-                            $auth->setAuthenticated($user);
-                            $this->redirectNow($redirectUrl);
-                        }
-                    } catch (Exception $e) {
-                        Logger::error(
-                            new Exception(
-                                'Cannot authenticate against backend "' . $backend->getName() . '".'
-                                . ' An exception was thrown:', 0, $e
-                            )
-                        );
-                        ++$backendsWithError;
+                    $authenticated = $backend->authenticate($user, $this->view->form->getValue('password'));
+                    if ($authenticated === true) {
+                        $auth->setAuthenticated($user);
+                        $this->redirectNow($redirectUrl);
+                    } elseif ($authenticated === null) {
+                        $backendsWithError += 1;
                     }
+                    $backendsTried += 1;
                 }
+
                 if ($backendsWithError === $backendsTried) {
                     throw new ConfigurationError(
                         'No authentication methods available. It seems that all set up authentication methods have'
                         . ' errors. Please contact your Icinga Web administrator'
                     );
                 }
+
                 $this->view->form->getElement('password')->addError(t('Incorrect username or password'));
             }
         } catch (Exception $e) {
@@ -140,4 +138,3 @@ class AuthenticationController extends ActionController
         }
     }
 }
-// @codingStandardsIgnoreEnd
diff --git a/library/Icinga/Authentication/Backend/DbUserBackend.php b/library/Icinga/Authentication/Backend/DbUserBackend.php
index 409fa4d06..03464adc7 100644
--- a/library/Icinga/Authentication/Backend/DbUserBackend.php
+++ b/library/Icinga/Authentication/Backend/DbUserBackend.php
@@ -29,12 +29,13 @@
 
 namespace Icinga\Authentication\Backend;
 
-use Exception;
-use Zend_Db_Expr;
+use \Exception;
+use \Zend_Db_Expr;
+use \Zend_Db_Select;
 use Icinga\Authentication\UserBackend;
 use Icinga\Data\Db\Connection;
+use Icinga\Logger\Logger;
 use Icinga\User;
-use \Zend_Db_Select;
 
 class DbUserBackend extends UserBackend
 {
@@ -68,32 +69,42 @@ class DbUserBackend extends UserBackend
     }
 
     /**
-     * Authenticate
+     * Authenticate the given user and return true on success, false on failure and null on error
      *
      * @param   User        $user
      * @param   string      $password
      *
-     * @return  bool
-     * @throws  \Exception              If we can not fetch the salt
+     * @return  bool|null
      */
     public function authenticate(User $user, $password)
     {
-        $salt = $this->getSalt($user->getUsername());
-        if ($salt === null) {
-            return false;
-        }
-        if ($salt === '') {
-            throw new Exception();
-        }
+        try {
+            $salt = $this->getSalt($user->getUsername());
+            if ($salt === null) {
+                return false;
+            }
+            if ($salt === '') {
+                throw new Exception('Cannot find salt for user ' . $user->getUsername());
+            }
 
-        $select = new Zend_Db_Select($this->conn->getConnection());
-        $row = $select->from('account', array(new Zend_Db_Expr(1)))
-            ->where('username = ?', $user->getUsername())
-            ->where('active = ?', true)
-            ->where('password = ?', $this->hashPassword($password, $salt))
-            ->query()->fetchObject();
+            $select = new Zend_Db_Select($this->conn->getConnection());
+            $row = $select->from('account', array(new Zend_Db_Expr(1)))
+                ->where('username = ?', $user->getUsername())
+                ->where('active = ?', true)
+                ->where('password = ?', $this->hashPassword($password, $salt))
+                ->query()->fetchObject();
 
-        return ($row !== false) ? true : false;
+            return ($row !== false) ? true : false;
+        } catch (Exception $e) {
+            Logger::error(
+                sprintf(
+                    'Failed to authenticate user "%s" with backend "%s". Exception occured: %s',
+                    $user->getUsername(),
+                    $this->getName(),
+                    $e->getMessage()
+                )
+            );
+        }
     }
 
     /**
diff --git a/library/Icinga/Authentication/Backend/LdapUserBackend.php b/library/Icinga/Authentication/Backend/LdapUserBackend.php
index 2e80302f1..f0922e092 100644
--- a/library/Icinga/Authentication/Backend/LdapUserBackend.php
+++ b/library/Icinga/Authentication/Backend/LdapUserBackend.php
@@ -29,7 +29,9 @@
 
 namespace Icinga\Authentication\Backend;
 
+use \Exception;
 use Icinga\User;
+use Icinga\Logger\Logger;
 use Icinga\Authentication\UserBackend;
 use Icinga\Protocol\Ldap\Connection;
 
@@ -87,23 +89,30 @@ class LdapUserBackend extends UserBackend
     }
 
     /**
-     * Authenticate
+     * Authenticate the given user and return true on success, false on failure and null on error
      *
      * @param   User    $user
      * @param   string  $password
      *
-     * @return  bool
+     * @return  bool|null
      */
     public function authenticate(User $user, $password)
     {
-        if ($this->conn->testCredentials(
+        try {
+            return $this->conn->testCredentials(
                 $this->conn->fetchDN($this->createQuery($user->getUsername())),
                 $password
-            )
-        ) {
-            return true;
+            );
+        } catch (Exception $e) {
+            Logger::error(
+                sprintf(
+                    'Failed to authenticate user "%s" with backend "%s". Exception occured: %s',
+                    $user->getUsername(),
+                    $this->getName(),
+                    $e->getMessage()
+                )
+            );
         }
-        return false;
     }
 
     /**