diff --git a/composer.json b/composer.json
index 8ae9f914a..32564bbee 100644
--- a/composer.json
+++ b/composer.json
@@ -45,7 +45,7 @@
         "phpstan/extension-installer": "^1.4",
         "phpunit/phpunit": "^11.5",
         "phpunit/php-invoker" : "^5.0",
-        "rector/rector": "^2.4"
+        "rector/rector": "^2.6"
     },
     "suggest" : {
         "hoa/bench"       : "If you would like to run the benchmark scripts"
diff --git a/lib/Component/VCard.php b/lib/Component/VCard.php
index 7c5ca739c..bbb852cc2 100644
--- a/lib/Component/VCard.php
+++ b/lib/Component/VCard.php
@@ -481,9 +481,7 @@ public function xmlSerialize(Xml\Writer $writer): void
         foreach ($this->children() as $property) {
             $group = $property->group;
 
-            if (!isset($propertiesByGroup[$group])) {
-                $propertiesByGroup[$group] = [];
-            }
+            $propertiesByGroup[$group] ??= [];
 
             $propertiesByGroup[$group][] = $property;
         }
diff --git a/lib/DateTimeParser.php b/lib/DateTimeParser.php
index 9469cacea..9b0c55b2e 100644
--- a/lib/DateTimeParser.php
+++ b/lib/DateTimeParser.php
@@ -63,9 +63,7 @@ public static function parseDate(string $date, ?\DateTimeZone $tz = null): \Date
             throw new InvalidDataException('The supplied iCalendar date value is incorrect: '.$date);
         }
 
-        if (is_null($tz)) {
-            $tz = new \DateTimeZone('UTC');
-        }
+        $tz ??= new \DateTimeZone('UTC');
 
         try {
             $date = new \DateTimeImmutable($matches[1].'-'.$matches[2].'-'.$matches[3], $tz);
diff --git a/lib/Document.php b/lib/Document.php
index 7cdb65d4f..8319b49be 100644
--- a/lib/Document.php
+++ b/lib/Document.php
@@ -146,9 +146,7 @@ public function createComponent(string $name, ?array $children = null, bool $def
         if (isset(static::$componentMap[$name])) {
             $class = static::$componentMap[$name];
         }
-        if (is_null($children)) {
-            $children = [];
-        }
+        $children ??= [];
 
         return new $class($this, $name, $children, $defaults);
     }
@@ -200,13 +198,9 @@ public function createProperty(string $name, $value = null, ?array $parameters =
         // we do not attempt to interpret or parse the datass value as specified in
         // https://datatracker.ietf.org/doc/html/rfc5545#section-3.2.20
         // So when we so far did not get a class-name, we use the default for the property
-        if (is_null($class)) {
-            $class = $this->getClassNameForPropertyName($name);
-        }
+        $class ??= $this->getClassNameForPropertyName($name);
 
-        if (is_null($parameters)) {
-            $parameters = [];
-        }
+        $parameters ??= [];
 
         return new $class($this, $name, $value, $parameters, $group, $lineIndex, $lineString);
     }
diff --git a/lib/FreeBusyGenerator.php b/lib/FreeBusyGenerator.php
index 3bcc842e3..9eec5c8d7 100644
--- a/lib/FreeBusyGenerator.php
+++ b/lib/FreeBusyGenerator.php
@@ -79,9 +79,7 @@ public function __construct(?\DateTimeInterface $start = null, ?\DateTimeInterfa
         if ($objects) {
             $this->setObjects($objects);
         }
-        if (is_null($timeZone)) {
-            $timeZone = new \DateTimeZone('UTC');
-        }
+        $timeZone ??= new \DateTimeZone('UTC');
         $this->setTimeZone($timeZone);
     }
 
diff --git a/lib/ITip/Broker.php b/lib/ITip/Broker.php
index 42862cd8b..19de8b16b 100644
--- a/lib/ITip/Broker.php
+++ b/lib/ITip/Broker.php
@@ -609,9 +609,7 @@ protected function parseEventForOrganizer(VCalendar $calendar, array $eventInfo,
 
                             // We're adding PARTSTAT=NEEDS-ACTION to ensure that
                             // iOS shows an "Inbox Item"
-                            if (!isset($currentEventAttendee['PARTSTAT'])) {
-                                $currentEventAttendee['PARTSTAT'] = 'NEEDS-ACTION';
-                            }
+                            $currentEventAttendee['PARTSTAT'] ??= 'NEEDS-ACTION';
                         }
                     }
 
diff --git a/lib/Parser/MimeDir.php b/lib/Parser/MimeDir.php
index 47fa972ce..1263ced8e 100644
--- a/lib/Parser/MimeDir.php
+++ b/lib/Parser/MimeDir.php
@@ -418,9 +418,7 @@ protected function readProperty(string $line)
             }
             if (isset($match['paramName'])) {
                 $lastParam = strtoupper($match['paramName']);
-                if (!isset($property['parameters'][$lastParam])) {
-                    $property['parameters'][$lastParam] = null;
-                }
+                $property['parameters'][$lastParam] ??= null;
                 $lastToken = self::TOKEN_PARAMNAME;
                 continue;
             }
@@ -440,9 +438,7 @@ protected function readProperty(string $line)
             // @codeCoverageIgnoreEnd
         }
 
-        if (\is_null($property['value'])) {
-            $property['value'] = '';
-        }
+        $property['value'] ??= '';
         if (!isset($property['name']) || 0 === strlen($property['name'])) {
             if ($this->options & self::OPTION_IGNORE_INVALID_LINES) {
                 return false;
diff --git a/lib/Recur/EventIterator.php b/lib/Recur/EventIterator.php
index d0317e14b..5db409350 100644
--- a/lib/Recur/EventIterator.php
+++ b/lib/Recur/EventIterator.php
@@ -91,9 +91,7 @@ class EventIterator implements \Iterator
      */
     public function __construct($input, ?string $uid = null, ?\DateTimeZone $timeZone = null)
     {
-        if (is_null($timeZone)) {
-            $timeZone = new \DateTimeZone('UTC');
-        }
+        $timeZone ??= new \DateTimeZone('UTC');
         $this->timeZone = $timeZone;
 
         if (is_array($input)) {
diff --git a/lib/TimeZoneUtil.php b/lib/TimeZoneUtil.php
index 2cd458578..19333e86a 100644
--- a/lib/TimeZoneUtil.php
+++ b/lib/TimeZoneUtil.php
@@ -41,9 +41,7 @@ private function __construct()
 
     private static function getInstance(): self
     {
-        if (null === self::$instance) {
-            self::$instance = new self();
-        }
+        self::$instance ??= new self();
 
         return self::$instance;
     }