diff --git a/system/libraries/Email.php b/system/libraries/Email.php
index 0e9cf05..48726b7 100644
--- a/system/libraries/Email.php
+++ b/system/libraries/Email.php
@@ -1036,7 +1036,8 @@
 	{
 		if (function_exists('idn_to_ascii') && $atpos = strpos($email, '@'))
 		{
-			$email = self::substr($email, 0, ++$atpos).idn_to_ascii(self::substr($email, $atpos));
+			$variant = defined('INTL_IDNA_VARIANT_UTS46') ? INTL_IDNA_VARIANT_UTS46 : INTL_IDNA_VARIANT_2003;
+			$email = self::substr($email, 0, ++$atpos).idn_to_ascii(self::substr($email, $atpos), $variant);
 		}
 
 		return (bool) filter_var($email, FILTER_VALIDATE_EMAIL);
@@ -1853,7 +1854,8 @@
 	{
 		if (function_exists('idn_to_ascii') && $atpos = strpos($email, '@'))
 		{
-			$email = self::substr($email, 0, ++$atpos).idn_to_ascii(self::substr($email, $atpos));
+			$variant = defined('INTL_IDNA_VARIANT_UTS46') ? INTL_IDNA_VARIANT_UTS46 : INTL_IDNA_VARIANT_2003;
+			$email = self::substr($email, 0, ++$atpos).idn_to_ascii(self::substr($email, $atpos), $variant);
 		}
 
 		return (filter_var($email, FILTER_VALIDATE_EMAIL) === $email && preg_match('#\A[a-z0-9._+-]+@[a-z0-9.-]{1,253}\z#i', $email));
diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index 71d0e64..1619ec9 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -1231,7 +1231,8 @@
 	{
 		if (function_exists('idn_to_ascii') && preg_match('#\A([^@]+)@(.+)\z#', $str, $matches))
 		{
-			$str = $matches[1].'@'.idn_to_ascii($matches[2]);
+			$variant = defined('INTL_IDNA_VARIANT_UTS46') ? INTL_IDNA_VARIANT_UTS46 : INTL_IDNA_VARIANT_2003;
+			$str = $matches[1].'@'.idn_to_ascii($matches[2], $variant);
 		}
 
 		return (bool) filter_var($str, FILTER_VALIDATE_EMAIL);
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index d222e17..647fe48 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -7,6 +7,11 @@
 
 Release Date: Not Released
 
+-  General Changes
+
+   -  Updated :doc:`Form Validation Library <libraries/form_validation>` rule ``valid_email`` to use ``INTL_IDNA_VARIANT_UCS46`` for non-ASCII domain names.
+   -  Updated :doc:`Email Library <libraries/email>` to use ``INTL_IDNA_VARIANT_UCS46`` for non-ASCII domain names.
+
 Bug fixes for 3.1.7
 -------------------