diff --git a/main/admin/user_import.php b/main/admin/user_import.php
index 42a808a4f3..813c616b88 100644
--- a/main/admin/user_import.php
+++ b/main/admin/user_import.php
@@ -335,7 +335,7 @@ function parse_csv_data($users, $fileName, $sendEmail = 0, $checkUniqueEmail = t
             }
         }
         $counter++;
-        if (isset($user['UserName'])) {
+        if (empty($user['UserName'])) {
             if ($allowRandom) {
                 $username = $generator->generateString(10, $chars);
                 $user['UserName'] = $username;
diff --git a/main/inc/ajax/install.ajax.php b/main/inc/ajax/install.ajax.php
index 7f4a755285..f19ad2fe2c 100755
--- a/main/inc/ajax/install.ajax.php
+++ b/main/inc/ajax/install.ajax.php
@@ -72,10 +72,7 @@ switch ($action) {
                 ];
 
                 $client = new GuzzleHttp\Client();
-                $url .= '?';
-                foreach ($data as $k => $v) {
-                    $url .= urlencode($k).'='.urlencode($v).'&';
-                }
+                $options['query'] = $data;
                 $res = $client->request('GET', $url, $options);
                 if ($res->getStatusCode() == '200') {
                     echo '1';
diff --git a/main/inc/lib/UnserializeApi.php b/main/inc/lib/UnserializeApi.php
index 4befaea250..45f19a6405 100644
--- a/main/inc/lib/UnserializeApi.php
+++ b/main/inc/lib/UnserializeApi.php
@@ -2,6 +2,7 @@
 /* For licensing terms, see /license.txt */
 
 use Brumann\Polyfill\Unserialize;
+use Fhaculty\Graph\Edge\Base;
 
 /**
  * Class UnserializeApi.
@@ -29,6 +30,10 @@ class UnserializeApi
                     \Fhaculty\Graph\Set\VerticesMap::class,
                     \Fhaculty\Graph\Set\Vertices::class,
                     \Fhaculty\Graph\Set\Edges::class,
+                    \Fhaculty\Graph\Vertex::class,
+                    \Fhaculty\Graph\Edge\Base::class,
+                    \Fhaculty\Graph\Edge\Directed::class,
+                    \Fhaculty\Graph\Edge\Undirected::class,
                 ];
                 break;
             case 'course':
diff --git a/src/Chamilo/CoreBundle/Entity/Sequence.php b/src/Chamilo/CoreBundle/Entity/Sequence.php
index 7687a4f9c8..e3d1b3a98e 100644
--- a/src/Chamilo/CoreBundle/Entity/Sequence.php
+++ b/src/Chamilo/CoreBundle/Entity/Sequence.php
@@ -135,7 +135,7 @@ class Sequence
      */
     public function getUnSerializeGraph()
     {
-        return UnserializeApi::unserialize('sequence_graph', $this->graph);
+        return \UnserializeApi::unserialize('sequence_graph', $this->graph);
     }
 
     /**
diff --git a/src/Chamilo/CourseBundle/Component/CourseCopy/Course.php b/src/Chamilo/CourseBundle/Component/CourseCopy/Course.php
index c03b218d83..113a3ff833 100644
--- a/src/Chamilo/CourseBundle/Component/CourseCopy/Course.php
+++ b/src/Chamilo/CourseBundle/Component/CourseCopy/Course.php
@@ -379,7 +379,7 @@ class Course
         if (extension_loaded('igbinary')) {
             $unserialized = igbinary_unserialize($course);
         } else {
-            $unserialized = UnserializeApi::unserialize(
+            $unserialized = \UnserializeApi::unserialize(
                 'course',
                 $course
             );
diff --git a/src/Chamilo/CourseBundle/Component/CourseCopy/CourseArchiver.php b/src/Chamilo/CourseBundle/Component/CourseCopy/CourseArchiver.php
index 2d1f64d107..80fe2c4f18 100644
--- a/src/Chamilo/CourseBundle/Component/CourseCopy/CourseArchiver.php
+++ b/src/Chamilo/CourseBundle/Component/CourseCopy/CourseArchiver.php
@@ -344,7 +344,7 @@ class CourseArchiver
         class_alias('Chamilo\CourseBundle\Component\CourseCopy\Resources\Work', 'Work');
 
         /** @var Course $course */
-        $course = UnserializeApi::unserialize('course', base64_decode($contents));
+        $course = \UnserializeApi::unserialize('course', base64_decode($contents));
 
         if (!in_array(
             get_class($course),
diff --git a/src/Chamilo/PageBundle/Entity/User.php b/src/Chamilo/PageBundle/Entity/User.php
index 194b91d87e..c1aca2ab2c 100644
--- a/src/Chamilo/PageBundle/Entity/User.php
+++ b/src/Chamilo/PageBundle/Entity/User.php
@@ -2282,7 +2282,7 @@ class User extends BaseUser
      */
     public function unserialize($serialized)
     {
-        $data = UnserializeApi::unserialize('not_allowed_classes', $serialized);
+        $data = \UnserializeApi::unserialize('not_allowed_classes', $serialized);
         // add a few extra elements in the array to ensure that we have enough keys when unserializing
         // older data which does not include all properties.
         $data = array_merge($data, array_fill(0, 2, null));