diff --git a/Classes/Command/SequenceCommandController.php b/Classes/Command/SequenceCommandController.php
index 076cd53..da8a129 100644
--- a/Classes/Command/SequenceCommandController.php
+++ b/Classes/Command/SequenceCommandController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace DigiComp\Sequence\Command;
 
 use DigiComp\Sequence\Service\SequenceGenerator;
diff --git a/Classes/Domain/Model/Insert.php b/Classes/Domain/Model/Insert.php
index 6e95e41..9e1a0fc 100644
--- a/Classes/Domain/Model/Insert.php
+++ b/Classes/Domain/Model/Insert.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace DigiComp\Sequence\Domain\Model;
 
 use Doctrine\ORM\Mapping as ORM;
@@ -20,20 +22,20 @@ class Insert
      * @Flow\Identity
      * @ORM\Id
      */
-    protected $number;
+    protected int $number;
 
     /**
      * @var string
      * @Flow\Identity
      * @ORM\Id
      */
-    protected $type;
+    protected string $type;
 
     /**
      * @param int $number
      * @param string|object $type
      */
-    public function __construct($number, $type)
+    public function __construct(int $number, $type)
     {
         $this->setNumber($number);
         $this->setType($type);
@@ -42,7 +44,7 @@ class Insert
     /**
      * @return int
      */
-    public function getNumber()
+    public function getNumber(): int
     {
         return $this->number;
     }
@@ -50,7 +52,7 @@ class Insert
     /**
      * @param int $number
      */
-    public function setNumber($number)
+    public function setNumber(int $number): void
     {
         $this->number = $number;
     }
@@ -58,7 +60,7 @@ class Insert
     /**
      * @return string
      */
-    public function getType()
+    public function getType(): string
     {
         return $this->type;
     }
@@ -66,7 +68,7 @@ class Insert
     /**
      * @param string|object $type
      */
-    public function setType($type)
+    public function setType($type): void
     {
         if (is_object($type)) {
             $type = get_class($type);
diff --git a/Classes/Service/Exception.php b/Classes/Service/Exception.php
index 37b66ed..96a3ad7 100644
--- a/Classes/Service/Exception.php
+++ b/Classes/Service/Exception.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace DigiComp\Sequence\Service;
 
 /**
diff --git a/Classes/Service/SequenceGenerator.php b/Classes/Service/SequenceGenerator.php
index 2477e1f..cdbc9d6 100644
--- a/Classes/Service/SequenceGenerator.php
+++ b/Classes/Service/SequenceGenerator.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace DigiComp\Sequence\Service;
 
 use DigiComp\Sequence\Domain\Model\Insert;
@@ -36,7 +38,7 @@ class SequenceGenerator
      * @param string|object $type
      * @return int
      */
-    public function getNextNumberFor($type)
+    public function getNextNumberFor($type): int
     {
         $type = $this->inferTypeFromSource($type);
         $count = $this->getLastNumberFor($type);
@@ -55,7 +57,7 @@ class SequenceGenerator
      * @param string|object $type
      * @return bool
      */
-    protected function validateFreeNumber($count, $type)
+    protected function validateFreeNumber(int $count, $type)
     {
         /* @var EntityManager $em */
         $em = $this->entityManager;
@@ -83,7 +85,7 @@ class SequenceGenerator
      * @param string|object $type
      * @return bool
      */
-    public function advanceTo($to, $type)
+    public function advanceTo(int $to, $type): bool
     {
         $type = $this->inferTypeFromSource($type);
 
@@ -94,12 +96,12 @@ class SequenceGenerator
      * @param string|object $type
      * @return int
      */
-    public function getLastNumberFor($type)
+    public function getLastNumberFor($type): int
     {
         /* @var EntityManager $em */
         $em = $this->entityManager;
 
-        return $em->getConnection()->executeQuery(
+        return (int) $em->getConnection()->executeQuery(
             'SELECT MAX(number) FROM ' . $em->getClassMetadata(Insert::class)->getTableName() . ' WHERE type = :type',
             ['type' => $this->inferTypeFromSource($type)]
         )->fetchAll(\PDO::FETCH_COLUMN)[0];
@@ -110,7 +112,7 @@ class SequenceGenerator
      * @return string
      * @throws Exception
      */
-    protected function inferTypeFromSource($stringOrObject)
+    protected function inferTypeFromSource($stringOrObject): string
     {
         if (is_object($stringOrObject)) {
             $stringOrObject = TypeHandling::getTypeForValue($stringOrObject);
diff --git a/composer.json b/composer.json
index 8f5d667..6e5e1c3 100644
--- a/composer.json
+++ b/composer.json
@@ -19,7 +19,8 @@
     "license": "MIT",
     "homepage": "https://github.com/digicomp/DigiComp.Sequence",
     "require": {
-        "neos/flow": "~4.1|~5.3|~6.3"
+        "neos/flow": "~5.3 | ^6.3.5",
+        "php": "^7.4"
     },
     "require-dev": {
         "phpunit/phpunit": "3.7.*",
@@ -33,7 +34,7 @@
     "extra": {
         "branch-alias": {
             "dev-version/1.x-dev": "1.1.x-dev",
-            "dev-develop": "2.0.x-dev"
+            "dev-develop": "3.0.x-dev"
         },
         "applied-flow-migrations": [
             "Inwebs.Basket-201409170938",