diff --git a/src/MD_STD.php b/src/MD_STD.php
index 1c3f9c8..1ca8792 100644
--- a/src/MD_STD.php
+++ b/src/MD_STD.php
@@ -234,7 +234,7 @@ final class MD_STD {
      *
      * @param array<mixed> $value   The value being encoded. Can be any type except a resource.
      * @param integer      $options Bitmask consisting of JSON_FORCE_OBJECT, JSON_HEX_QUOT ...
-     * @param integer      $depth   Depth of coding.
+     * @param positive-int $depth   Depth of coding.
      *
      * @return string
      */
@@ -253,9 +253,9 @@ final class MD_STD {
      *
      * @see https://www.php.net/manual/en/function.json-encode.php
      *
-     * @param object  $value   The value being encoded. Can be any type except a resource.
-     * @param integer $options Bitmask consisting of JSON_FORCE_OBJECT, JSON_HEX_QUOT ...
-     * @param integer $depth   Depth of coding.
+     * @param object       $value   The value being encoded. Can be any type except a resource.
+     * @param integer      $options Bitmask consisting of JSON_FORCE_OBJECT, JSON_HEX_QUOT ...
+     * @param positive-int $depth   Depth of coding.
      *
      * @return string
      */