diff --git a/src/file/csv/SsBuilder.php b/src/file/csv/SsBuilder.php
index 6525f02..717c010 100644
--- a/src/file/csv/SsBuilder.php
+++ b/src/file/csv/SsBuilder.php
@@ -3,7 +3,6 @@ namespace nur\sery\file\csv;
 
 use nur\sery\ext\spreadsheet\wsutils;
 use nur\sery\os\path;
-use nur\sery\ValueException;
 use nur\sery\web\http;
 use PhpOffice\PhpSpreadsheet\Cell\IValueBinder;
 use PhpOffice\PhpSpreadsheet\Cell\StringValueBinder;
@@ -42,22 +41,13 @@ class SsBuilder extends AbstractBuilder {
 
   protected int $rowStyle;
 
-  function setWsname(?string $wsname): void {
+  function setWsname(?string $wsname): self {
     $ss = $this->ss;
     $this->ws = null;
     $this->nrow = 0;
     $this->rowStyle = self::STYLE_ROW;
-    if ($wsname === null) {
-      $ws = $ss->getActiveSheet();
-    } elseif (is_numeric($wsname)) {
-      $sheetCount = $ss->getSheetCount();
-      if ($wsname < 1 || $wsname > $sheetCount) {
-        throw ValueException::invalid_value($wsname, "sheet index");
-      }
-      $ws = $ss->getSheet($wsname - 1);
-    } else {
-      $ws = $ss->getSheetByName($wsname);
-    }
+
+    $ws = wsutils::get_ws($wsname, $ss);
     if ($ws === null) {
       $ws = $ss->createSheet()->setTitle($wsname);
       $this->wroteHeaders = false;
@@ -67,6 +57,7 @@ class SsBuilder extends AbstractBuilder {
       $this->wroteHeaders = $maxRow > 1;
     }
     $this->ws = $ws;
+    return $this;
   }
 
   function _write(array $row): void {
diff --git a/src/file/csv/SsReader.php b/src/file/csv/SsReader.php
index 0321b83..992e577 100644
--- a/src/file/csv/SsReader.php
+++ b/src/file/csv/SsReader.php
@@ -9,6 +9,7 @@ use nur\sery\php\time\DateTime;
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
 use PhpOffice\PhpSpreadsheet\IOFactory;
 use PhpOffice\PhpSpreadsheet\RichText\RichText;
+use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
 
 class SsReader extends AbstractReader {
   use TAbstractReader;
@@ -58,9 +59,10 @@ class SsReader extends AbstractReader {
     $this->wsname = $params["wsname"] ?? static::WSNAME;
   }
 
-  protected ?string $wsname;
+  /** @var string|int|null */
+  protected $wsname;
 
-  function setWsname(?string $wsname): self {
+  function setWsname($wsname): self {
     $this->wsname = $wsname;
     return $this;
   }