diff --git a/src/spout/SpoutBuilder.php b/src/spout/SpoutBuilder.php
index 784ecc3..b655128 100644
--- a/src/spout/SpoutBuilder.php
+++ b/src/spout/SpoutBuilder.php
@@ -234,11 +234,11 @@ class SpoutBuilder extends AbstractBuilder {
 
   protected ?bool $differentOddEven = null;
 
-  protected int $oddEvenIndex = 1;
+  protected int $oddEvenIndex = 0;
 
-  function setDifferentOddEven(bool $differentOddEven, bool $startWithOdd=true): self {
+  function setDifferentOddEven(bool $differentOddEven, ?bool $startWithOdd=null): self {
     $this->differentOddEven = $differentOddEven;
-    if ($differentOddEven) $this->oddEvenIndex = $startWithOdd? 1: 0;
+    if ($differentOddEven && $startWithOdd !== null) $this->oddEvenIndex = $startWithOdd? 1: 0;
     return $this;
   }