diff --git a/Resources/migrations/Version20141128194409.php b/migrations/Version20141128194409.php
similarity index 97%
rename from Resources/migrations/Version20141128194409.php
rename to migrations/Version20141128194409.php
index fe44997f7..6731826a4 100644
--- a/Resources/migrations/Version20141128194409.php
+++ b/migrations/Version20141128194409.php
@@ -2,7 +2,7 @@
 
 namespace Application\Migrations;
 
-use Doctrine\DBAL\Migrations\AbstractMigration;
+use Doctrine\Migrations\AbstractMigration;
 use Doctrine\DBAL\Schema\Schema;
 
 /**
@@ -10,7 +10,7 @@ use Doctrine\DBAL\Schema\Schema;
  */
 class Version20141128194409 extends AbstractMigration
 {
-    public function up(Schema $schema)
+    public function up(Schema $schema): void
     {
         $this->addSql("CREATE TABLE Country (id INT NOT NULL, name JSON NOT NULL, countryCode VARCHAR(3) NOT NULL, PRIMARY KEY(id));");
         $this->addSql("CREATE TABLE centers (id INT NOT NULL, name VARCHAR(255) NOT NULL, PRIMARY KEY(id));");
@@ -48,7 +48,7 @@ class Version20141128194409 extends AbstractMigration
         $this->addSql("ALTER TABLE user_groupcenter ADD CONSTRAINT FK_33FFE54A7EC2FA68 FOREIGN KEY (groupcenter_id) REFERENCES group_centers (id) ON DELETE CASCADE NOT DEFERRABLE INITIALLY IMMEDIATE;");
     }
 
-    public function down(Schema $schema)
+    public function down(Schema $schema): void
     {
         // this down() migration is auto-generated, please modify it to your needs
 
diff --git a/Resources/migrations/Version20150821105642.php b/migrations/Version20150821105642.php
similarity index 90%
rename from Resources/migrations/Version20150821105642.php
rename to migrations/Version20150821105642.php
index 211532c93..3880178b1 100644
--- a/Resources/migrations/Version20150821105642.php
+++ b/migrations/Version20150821105642.php
@@ -2,7 +2,7 @@
 
 namespace Application\Migrations;
 
-use Doctrine\DBAL\Migrations\AbstractMigration;
+use Doctrine\Migrations\AbstractMigration;
 use Doctrine\DBAL\Schema\Schema;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Doctrine\ORM\Query\ResultSetMapping;
@@ -28,7 +28,7 @@ class Version20150821105642 extends AbstractMigration implements
     /**
      * @param Schema $schema
      */
-    public function up(Schema $schema)
+    public function up(Schema $schema): void
     {
         // this up() migration is auto-generated, please modify it to your needs
         $this->abortIf($this->connection->getDatabasePlatform()->getName() != 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');
@@ -39,8 +39,20 @@ class Version20150821105642 extends AbstractMigration implements
 
     }
     
-    public function postUp(Schema $schema)
+    public function postUp(Schema $schema): void
     {
+        /*
+         * Before the upgrade to symfony version 4, this code worked.
+         * 
+         * But it doesn't work any more after the migration and currently this
+         * code should note be necessary.
+         * 
+         * This code is kept for reference, and may be re-activated if needed, but
+         * the probability that this will happens is near 0
+         */
+        return;
+        
+        
         //transform data from groupcenter_permissionsgroup table
         $em = $this->container->get('doctrine.orm.entity_manager');
         
@@ -110,7 +122,7 @@ class Version20150821105642 extends AbstractMigration implements
     /**
      * @param Schema $schema
      */
-    public function down(Schema $schema)
+    public function down(Schema $schema): void
     {
         $this->abortIf($this->connection->getDatabasePlatform()->getName() != 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');
 
diff --git a/Resources/migrations/Version20150821122935.php b/migrations/Version20150821122935.php
similarity index 91%
rename from Resources/migrations/Version20150821122935.php
rename to migrations/Version20150821122935.php
index 38a4f1b5f..9e290c9df 100644
--- a/Resources/migrations/Version20150821122935.php
+++ b/migrations/Version20150821122935.php
@@ -2,7 +2,7 @@
 
 namespace Application\Migrations;
 
-use Doctrine\DBAL\Migrations\AbstractMigration;
+use Doctrine\Migrations\AbstractMigration;
 use Doctrine\DBAL\Schema\Schema;
 
 /**
@@ -14,7 +14,7 @@ class Version20150821122935 extends AbstractMigration
     /**
      * @param Schema $schema
      */
-    public function up(Schema $schema)
+    public function up(Schema $schema): void
     {
         
         $this->addSql('DROP TABLE groupcenter_permissionsgroup');
@@ -25,7 +25,7 @@ class Version20150821122935 extends AbstractMigration
     /**
      * @param Schema $schema
      */
-    public function down(Schema $schema)
+    public function down(Schema $schema): void
     {
         $this->addSql('ALTER TABLE group_centers ALTER permissionsGroup_id SET DEFAULT NULL');
         $this->addSql('CREATE TABLE groupcenter_permissionsgroup (groupcenter_id INT NOT NULL, permissionsgroup_id INT NOT NULL, PRIMARY KEY(groupcenter_id, permissionsgroup_id))');
diff --git a/Resources/migrations/Version20160310122322.php b/migrations/Version20160310122322.php
similarity index 94%
rename from Resources/migrations/Version20160310122322.php
rename to migrations/Version20160310122322.php
index 566dc7f79..7e4b9d95f 100644
--- a/Resources/migrations/Version20160310122322.php
+++ b/migrations/Version20160310122322.php
@@ -2,7 +2,7 @@
 
 namespace Application\Migrations;
 
-use Doctrine\DBAL\Migrations\AbstractMigration;
+use Doctrine\Migrations\AbstractMigration;
 use Doctrine\DBAL\Schema\Schema;
 
 /**
@@ -13,7 +13,7 @@ class Version20160310122322 extends AbstractMigration
     /**
      * @param Schema $schema
      */
-    public function up(Schema $schema)
+    public function up(Schema $schema): void
     {
         $this->abortIf($this->connection->getDatabasePlatform()->getName() != 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');
 
@@ -52,7 +52,7 @@ class Version20160310122322 extends AbstractMigration
     /**
      * @param Schema $schema
      */
-    public function down(Schema $schema)
+    public function down(Schema $schema): void
     {
         $this->abortIf($this->connection->getDatabasePlatform()->getName() != 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');
 
diff --git a/Resources/migrations/Version20180703191509.php b/migrations/Version20180703191509.php
similarity index 87%
rename from Resources/migrations/Version20180703191509.php
rename to migrations/Version20180703191509.php
index 82117de9d..03f13a532 100644
--- a/Resources/migrations/Version20180703191509.php
+++ b/migrations/Version20180703191509.php
@@ -2,7 +2,7 @@
 
 namespace Application\Migrations;
 
-use Doctrine\DBAL\Migrations\AbstractMigration;
+use Doctrine\Migrations\AbstractMigration;
 use Doctrine\DBAL\Schema\Schema;
 
 /**
@@ -10,7 +10,7 @@ use Doctrine\DBAL\Schema\Schema;
  */
 final class Version20180703191509 extends AbstractMigration
 {
-    public function up(Schema $schema) : void
+    public function up(Schema $schema): void
     {
         $this->abortIf($this->connection->getDatabasePlatform()->getName() !== 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');
 
@@ -23,7 +23,7 @@ final class Version20180703191509 extends AbstractMigration
         
     }
 
-    public function down(Schema $schema) : void
+    public function down(Schema $schema): void
     {
         $this->abortIf($this->connection->getDatabasePlatform()->getName() !== 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');
 
diff --git a/Resources/migrations/Version20180709181423.php b/migrations/Version20180709181423.php
similarity index 95%
rename from Resources/migrations/Version20180709181423.php
rename to migrations/Version20180709181423.php
index 93ca04e12..40b9f853f 100644
--- a/Resources/migrations/Version20180709181423.php
+++ b/migrations/Version20180709181423.php
@@ -2,7 +2,7 @@
 
 namespace Application\Migrations;
 
-use Doctrine\DBAL\Migrations\AbstractMigration;
+use Doctrine\Migrations\AbstractMigration;
 use Doctrine\DBAL\Schema\Schema;
 
 /**
@@ -11,7 +11,7 @@ use Doctrine\DBAL\Schema\Schema;
  */
 final class Version20180709181423 extends AbstractMigration
 {
-    public function up(Schema $schema) : void
+    public function up(Schema $schema): void
     {
         $this->abortIf($this->connection->getDatabasePlatform()->getName() !== 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');
 
@@ -69,7 +69,7 @@ SQL
             );
     }
 
-    public function down(Schema $schema) : void
+    public function down(Schema $schema): void
     {
         $this->abortIf($this->connection->getDatabasePlatform()->getName() !== 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');
         
diff --git a/Resources/migrations/Version20180905101426.php b/migrations/Version20180905101426.php
similarity index 87%
rename from Resources/migrations/Version20180905101426.php
rename to migrations/Version20180905101426.php
index 2f7d1afc2..e8aafd57b 100644
--- a/Resources/migrations/Version20180905101426.php
+++ b/migrations/Version20180905101426.php
@@ -10,14 +10,14 @@ use Doctrine\Migrations\AbstractMigration;
  */
 final class Version20180905101426 extends AbstractMigration
 {
-    public function up(Schema $schema) : void
+    public function up(Schema $schema): void
     {
         $this->addSql('ALTER TABLE permission_groups ADD flags JSONB DEFAULT \'[]\' NOT NULL');
         $this->addSql('ALTER TABLE group_centers ALTER permissionsgroup_id DROP NOT NULL');
 
     }
 
-    public function down(Schema $schema) : void
+    public function down(Schema $schema): void
     {
         $this->addSql('ALTER TABLE permission_groups DROP COLUMN flags');
         $this->addSql('ALTER TABLE group_centers ALTER permissionsgroup_id SET DEFAULT NULL'); 
diff --git a/Resources/migrations/Version20180911093642.php b/migrations/Version20180911093642.php
similarity index 91%
rename from Resources/migrations/Version20180911093642.php
rename to migrations/Version20180911093642.php
index 09031278d..c2fefa5f3 100644
--- a/Resources/migrations/Version20180911093642.php
+++ b/migrations/Version20180911093642.php
@@ -10,7 +10,7 @@ use Doctrine\Migrations\AbstractMigration;
  */
 final class Version20180911093642 extends AbstractMigration
 {
-    public function up(Schema $schema) : void
+    public function up(Schema $schema): void
     {
         $this->addSql("DROP TRIGGER canonicalize_user_on_update ON users");
         
@@ -26,7 +26,7 @@ SQL
 
     }
 
-    public function down(Schema $schema) : void
+    public function down(Schema $schema): void
     {
         $this->addSql("DROP TRIGGER canonicalize_user_on_update ON users");
             
diff --git a/Resources/migrations/Version20200422122715.php b/migrations/Version20200422122715.php
similarity index 83%
rename from Resources/migrations/Version20200422122715.php
rename to migrations/Version20200422122715.php
index 2ce63b41a..4f5b58105 100644
--- a/Resources/migrations/Version20200422122715.php
+++ b/migrations/Version20200422122715.php
@@ -10,12 +10,12 @@ use Doctrine\Migrations\AbstractMigration;
  */
 final class Version20200422122715 extends AbstractMigration
 {
-    public function up(Schema $schema) : void
+    public function up(Schema $schema): void
     {
         $this->addSql('ALTER TABLE chill_main_address ADD isNoAddress BOOLEAN NOT NULL DEFAULT FALSE');
     }
 
-    public function down(Schema $schema) : void
+    public function down(Schema $schema): void
     {
         $this->addSql('ALTER TABLE chill_main_address DROP isNoAddress');
     }