diff --git a/application/Espo/Core/Utils/DateTime.php b/application/Espo/Core/Utils/DateTime.php
index 475d03fe13..8a73c0ad93 100644
--- a/application/Espo/Core/Utils/DateTime.php
+++ b/application/Espo/Core/Utils/DateTime.php
@@ -44,13 +44,13 @@ class DateTime
 
     public const SYSTEM_DATE_FORMAT = 'Y-m-d';
 
-    private $dateFormat;
+    private ?string $dateFormat;
 
-    private $timeFormat;
+    private ?string $timeFormat;
 
-    private $timezone;
+    private DateTimeZone $timezone;
 
-    private $language;
+    private ?string $language;
 
     public function __construct(
         ?string $dateFormat = 'YYYY-MM-DD',
@@ -240,6 +240,7 @@ class DateTime
 
     /**
      * @deprecated Use `convertSystemDate`.
+     * @param string $string
      */
     public function convertSystemDateToGlobal($string): ?string
     {
diff --git a/application/Espo/Core/Utils/File/Unifier.php b/application/Espo/Core/Utils/File/Unifier.php
index 9039876f1b..ae16fe96ff 100644
--- a/application/Espo/Core/Utils/File/Unifier.php
+++ b/application/Espo/Core/Utils/File/Unifier.php
@@ -42,17 +42,15 @@ use JsonException;
 
 class Unifier
 {
-    private $fileManager;
+    private FileManager $fileManager;
 
-    private $module;
+    private Module $module;
 
-    private $pathProvider;
+    private PathProvider $pathProvider;
 
-    protected $useObjects = false;
+    protected bool $useObjects = false;
 
-    private $unsetFileName = 'unset.json';
-
-    private $moduleList = null;
+    private string $unsetFileName = 'unset.json';
 
     public function __construct(FileManager $fileManager, Module $module, PathProvider $pathProvider)
     {
@@ -64,7 +62,7 @@ class Unifier
     /**
      * Merge data of resource files.
      *
-     * @return array|object
+     * @return array<string,mixed>|\stdClass
      */
     public function unify(string $path, bool $noCustom = false)
     {
@@ -110,6 +108,9 @@ class Unifier
         );
     }
 
+    /**
+     * @return array<string,mixed>
+     */
     private function unifySingle(string $dirPath, bool $recursively)
     {
         $data = [];
@@ -180,6 +181,10 @@ class Unifier
         return Util::unsetInArray($data, $unsets);
     }
 
+    /**
+     * @return \stdClass|array<string,mixed>
+     * @throws JsonException
+     */
     private function getContents(string $path)
     {
         $fileContent = $this->fileManager->getContents($path);
diff --git a/application/Espo/Core/Utils/File/UnifierObj.php b/application/Espo/Core/Utils/File/UnifierObj.php
index 8ef60a8558..ce43291d80 100644
--- a/application/Espo/Core/Utils/File/UnifierObj.php
+++ b/application/Espo/Core/Utils/File/UnifierObj.php
@@ -31,5 +31,5 @@ namespace Espo\Core\Utils\File;
 
 class UnifierObj extends Unifier
 {
-    protected $useObjects = true;
+    protected bool $useObjects = true;
 }
diff --git a/application/Espo/Core/Utils/Hasher.php b/application/Espo/Core/Utils/Hasher.php
index 82d4fee970..4411e5f1f0 100644
--- a/application/Espo/Core/Utils/Hasher.php
+++ b/application/Espo/Core/Utils/Hasher.php
@@ -37,9 +37,9 @@ use Espo\Core\Utils\Config;
  */
 class Hasher
 {
-    private $config;
+    private Config $config;
 
-    private $secretKeyParam = 'hashSecretKey';
+    private string $secretKeyParam = 'hashSecretKey';
 
     public function __construct(Config $config)
     {