diff --git a/src/MD_STD.php b/src/MD_STD.php
index 1ca8792..a7eac82 100644
--- a/src/MD_STD.php
+++ b/src/MD_STD.php
@@ -177,7 +177,7 @@ final class MD_STD {
     /**
      * Function checking if a string contains another in a case-insensitive way.
      *
-     * @param non-empty-string $haystack String to check.
+     * @param string           $haystack String to check.
      * @param non-empty-string $needle   Potential start of $haystack.
      *
      * @return boolean