diff --git a/src/Protocol/Imap/Request/SequenceSet.php b/src/Protocol/Imap/Request/SequenceSet.php
index 7f83cd2..c34da3d 100644
--- a/src/Protocol/Imap/Request/SequenceSet.php
+++ b/src/Protocol/Imap/Request/SequenceSet.php
@@ -6,10 +6,10 @@
 final class SequenceSet
 {
     /**
-     * @var array<int, mixed>
+     * @var array<int, string>
      */
     private $set = [];
-    
+
     private function __construct()
     {
         // this constructor is protected in order to force
@@ -23,7 +23,7 @@ private function __construct()
     public function withSingle(int $number): self
     {
         $set = clone $this;
-        $set->set[] = $number;
+        $set->set[] = (string)$number;
         return $set;
     }
 
@@ -86,7 +86,7 @@ public static function single(int $number): self
     public static function multiple(array $numbers): self
     {
         $set = new self();
-        $set->set = \array_map('strval', $numbers);
+        $set->set = \array_map(\strval(...), $numbers);
         return $set;
     }
 
diff --git a/src/Protocol/Imap/TagFactory/GeneratorTagFactory.php b/src/Protocol/Imap/TagFactory/GeneratorTagFactory.php
index 04f99b5..70cedcb 100644
--- a/src/Protocol/Imap/TagFactory/GeneratorTagFactory.php
+++ b/src/Protocol/Imap/TagFactory/GeneratorTagFactory.php
@@ -12,7 +12,7 @@ final class GeneratorTagFactory implements TagFactoryInterface
      * @var \Generator|Tag[]
      */
     private $iterator;
-    
+
     public function __construct()
     {
         $this->iterator = $this->newList();
@@ -37,7 +37,6 @@ private function newList(): \Generator
     {
         $i = 0;
 
-        /** @phpstan-ignore-next-line */
         while (true) {
             yield Tag::fromNonce(++$i);
         }