diff --git a/Admin/Routes/Web/Backend.php b/Admin/Routes/Web/Backend.php
index 0416e4e..9edb67f 100644
--- a/Admin/Routes/Web/Backend.php
+++ b/Admin/Routes/Web/Backend.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 use Modules\Checklist\Controller\BackendController;
 use Modules\Checklist\Models\PermissionState;
diff --git a/Theme/Backend/Lang/Navigation.en.lang.php b/Theme/Backend/Lang/Navigation.en.lang.php
index b7ce2a5..8a606db 100644
--- a/Theme/Backend/Lang/Navigation.en.lang.php
+++ b/Theme/Backend/Lang/Navigation.en.lang.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/Lang/api.en.lang.php b/Theme/Backend/Lang/api.en.lang.php
index b07f33e..2f59807 100644
--- a/Theme/Backend/Lang/api.en.lang.php
+++ b/Theme/Backend/Lang/api.en.lang.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/Lang/en.lang.php b/Theme/Backend/Lang/en.lang.php
index 0644e91..b6e6f03 100644
--- a/Theme/Backend/Lang/en.lang.php
+++ b/Theme/Backend/Lang/en.lang.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/checklist-list.tpl.php b/Theme/Backend/checklist-list.tpl.php
index 7ebf743..fcce038 100644
--- a/Theme/Backend/checklist-list.tpl.php
+++ b/Theme/Backend/checklist-list.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/checklist-template-create.tpl.php b/Theme/Backend/checklist-template-create.tpl.php
index de8aebf..e3fb99f 100644
--- a/Theme/Backend/checklist-template-create.tpl.php
+++ b/Theme/Backend/checklist-template-create.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/checklist-template-list.tpl.php b/Theme/Backend/checklist-template-list.tpl.php
index b9dd7eb..218bdf2 100644
--- a/Theme/Backend/checklist-template-list.tpl.php
+++ b/Theme/Backend/checklist-template-list.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *