diff --git a/.github/FUNDING.yml b/.github/FUNDING.yml
index c4c7a553..c67f2795 100644
--- a/.github/FUNDING.yml
+++ b/.github/FUNDING.yml
@@ -1,2 +1 @@
-github: # waiting to get approved to the beta
-custom: https://www.paypal.me/kackb00n
+github: sebastianfeldmann
diff --git a/.scrutinizer.yml b/.scrutinizer.yml
index 0569db7d..6b9d8754 100644
--- a/.scrutinizer.yml
+++ b/.scrutinizer.yml
@@ -15,6 +15,11 @@ build:
         coverage:
           file:  clover.xml
           format: php-clover
+  nodes:
+    analysis:
+      tests:
+        override:
+          - php-scrutinizer-run
 coding_style:
   php:
     spaces:
diff --git a/phpbu.xsd b/phpbu.xsd
index 450732f3..4ea9a814 100644
--- a/phpbu.xsd
+++ b/phpbu.xsd
@@ -73,6 +73,7 @@
           <xs:enumeration value="gzip"/>
           <xs:enumeration value="zip"/>
           <xs:enumeration value="7zip"/>
+          <xs:enumeration value="xz"/>
         </xs:restriction>
       </xs:simpleType>
     </xs:attribute>
diff --git a/phpstan.neon b/phpstan.neon
index 0246f42e..1582ad63 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,5 +1,5 @@
 parameters:
-  level: 2
+  level: 3
   paths:
   - %currentWorkingDirectory%/src/
   ignoreErrors:
diff --git a/src/Backup/Cleaner/Capacity.php b/src/Backup/Cleaner/Capacity.php
index 226a9c5d..b8798e28 100644
--- a/src/Backup/Cleaner/Capacity.php
+++ b/src/Backup/Cleaner/Capacity.php
@@ -64,7 +64,7 @@ public function setup(array $options)
      *
      * @param  \phpbu\App\Backup\Target    $target
      * @param  \phpbu\App\Backup\Collector $collector
-     * @return \phpbu\App\Backup\File\Local[]
+     * @return \phpbu\App\Backup\File[]
      * @throws \phpbu\App\Exception
      */
     protected function getFilesToDelete(Target $target, Collector $collector)
@@ -76,7 +76,7 @@ protected function getFilesToDelete(Target $target, Collector $collector)
 
 
         // sum up the size of all backups
-        /** @var \phpbu\App\Backup\File\Local $file */
+        /** @var \phpbu\App\Backup\File $file */
         foreach ($files as $file) {
             $size += $file->getSize();
         }
@@ -89,6 +89,9 @@ protected function getFilesToDelete(Target $target, Collector $collector)
             while ($this->isCapacityExceeded($size) && count($files) > 0) {
                 // get oldest backup from list, move it to delete list
                 $file = array_shift($files);
+                if ($file === null) {
+                    break;
+                }
                 $size -= $file->getSize();
                 $delete[] = $file;
             }
diff --git a/src/Backup/Cleaner/Quantity.php b/src/Backup/Cleaner/Quantity.php
index c8c15d4b..2c795943 100644
--- a/src/Backup/Cleaner/Quantity.php
+++ b/src/Backup/Cleaner/Quantity.php
@@ -53,7 +53,7 @@ public function setup(array $options)
      *
      * @param  \phpbu\App\Backup\Target    $target
      * @param  \phpbu\App\Backup\Collector $collector
-     * @return \phpbu\App\Backup\File\Local[]
+     * @return \phpbu\App\Backup\File[]
      */
     protected function getFilesToDelete(Target $target, Collector $collector)
     {
@@ -66,6 +66,9 @@ protected function getFilesToDelete(Target $target, Collector $collector)
 
             while ($this->isCapacityExceeded($files)) {
                 $file     = array_shift($files);
+                if ($file === null) {
+                    break;
+                }
                 $delete[] = $file;
             }
         }
diff --git a/src/Backup/Cleaner/Stepwise.php b/src/Backup/Cleaner/Stepwise.php
index d5647d61..8b3212bc 100644
--- a/src/Backup/Cleaner/Stepwise.php
+++ b/src/Backup/Cleaner/Stepwise.php
@@ -139,7 +139,7 @@ protected function setupRanges()
      *
      * @param  \phpbu\App\Backup\Target    $target
      * @param  \phpbu\App\Backup\Collector $collector
-     * @return \phpbu\App\Backup\File\Local[]
+     * @return \phpbu\App\Backup\File[]
      * @throws \phpbu\App\Exception
      */
     protected function getFilesToDelete(Target $target, Collector $collector)
diff --git a/src/Backup/Cleaner/Stepwise/Keeper/OnePerGroup.php b/src/Backup/Cleaner/Stepwise/Keeper/OnePerGroup.php
index e821c25e..db2ed962 100644
--- a/src/Backup/Cleaner/Stepwise/Keeper/OnePerGroup.php
+++ b/src/Backup/Cleaner/Stepwise/Keeper/OnePerGroup.php
@@ -27,7 +27,7 @@ class OnePerGroup implements Keeper
     /**
      * List of groups containing the files.
      *
-     * @var \phpbu\App\Backup\File\Local[]
+     * @var \phpbu\App\Backup\File\Local[][]
      */
     private $groups = [];
 
diff --git a/src/Backup/Collector/Abstraction.php b/src/Backup/Collector/Abstraction.php
index 3ec9ac8c..63756f6a 100644
--- a/src/Backup/Collector/Abstraction.php
+++ b/src/Backup/Collector/Abstraction.php
@@ -36,7 +36,7 @@ abstract class Abstraction
     /**
      * Collection cache
      *
-     * @var \phpbu\App\Backup\File\Local[]
+     * @var \phpbu\App\Backup\File[]
      */
     protected $files;
 
@@ -67,7 +67,7 @@ public function setSimulation(bool $isSimulation)
     /**
      * Get all created backups.
      *
-     * @return \phpbu\App\Backup\File\Local[]
+     * @return \phpbu\App\Backup\File[]
      */
     public function getBackupFiles() : array
     {
diff --git a/src/Configuration/Loader/File.php b/src/Configuration/Loader/File.php
index 1bfa70e1..7748a4b5 100644
--- a/src/Configuration/Loader/File.php
+++ b/src/Configuration/Loader/File.php
@@ -209,7 +209,7 @@ protected function getAdapterizedValue($value)
      *
      * @param  string $filename
      * @throws \phpbu\App\Exception
-     * @return \stdClass
+     * @return string
      */
     protected function loadFile($filename)
     {