diff --git a/Admin/Routes/Web/Backend.php b/Admin/Routes/Web/Backend.php
index e32f2e0..a59e28a 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\Accounting\Controller\BackendController;
 use Modules\Accounting\Models\PermissionState;
diff --git a/Theme/Backend/Lang/Navigation.en.lang.php b/Theme/Backend/Lang/Navigation.en.lang.php
index b918366..d16a798 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 959dc12..763b2bb 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 7797f9c..b4c5f7d 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/entries.tpl.php b/Theme/Backend/entries.tpl.php
index ba9b45f..5a610b5 100644
--- a/Theme/Backend/entries.tpl.php
+++ b/Theme/Backend/entries.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/gl-create.tpl.php b/Theme/Backend/gl-create.tpl.php
index d75c5ba..85dd0b0 100644
--- a/Theme/Backend/gl-create.tpl.php
+++ b/Theme/Backend/gl-create.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/gl-list.tpl.php b/Theme/Backend/gl-list.tpl.php
index 46b2f6e..985e2ee 100644
--- a/Theme/Backend/gl-list.tpl.php
+++ b/Theme/Backend/gl-list.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/gl-profile.tpl.php b/Theme/Backend/gl-profile.tpl.php
index 559f971..0bb3664 100644
--- a/Theme/Backend/gl-profile.tpl.php
+++ b/Theme/Backend/gl-profile.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/journal-list.tpl.php b/Theme/Backend/journal-list.tpl.php
index c34d022..39fca7b 100644
--- a/Theme/Backend/journal-list.tpl.php
+++ b/Theme/Backend/journal-list.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/stack-archive-list.tpl.php b/Theme/Backend/stack-archive-list.tpl.php
index f2be1d9..56a13b9 100644
--- a/Theme/Backend/stack-archive-list.tpl.php
+++ b/Theme/Backend/stack-archive-list.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/stack-create.tpl.php b/Theme/Backend/stack-create.tpl.php
index 7dafaad..9895439 100644
--- a/Theme/Backend/stack-create.tpl.php
+++ b/Theme/Backend/stack-create.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/stack-entries.tpl.php b/Theme/Backend/stack-entries.tpl.php
index 559f971..0bb3664 100644
--- a/Theme/Backend/stack-entries.tpl.php
+++ b/Theme/Backend/stack-entries.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/stack-list.tpl.php b/Theme/Backend/stack-list.tpl.php
index 0892213..765969f 100644
--- a/Theme/Backend/stack-list.tpl.php
+++ b/Theme/Backend/stack-list.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *
diff --git a/Theme/Backend/stack-predefined-list.tpl.php b/Theme/Backend/stack-predefined-list.tpl.php
index 5ad9a27..f19c50e 100644
--- a/Theme/Backend/stack-predefined-list.tpl.php
+++ b/Theme/Backend/stack-predefined-list.tpl.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 /**
  * Orange Management
  *