diff --git a/bin/update_hostname_validator.php b/bin/update_hostname_validator.php
index 69043d681..593f73a09 100644
--- a/bin/update_hostname_validator.php
+++ b/bin/update_hostname_validator.php
@@ -177,9 +177,12 @@ function getNewValidTlds($string)
 function getPunycodeDecoder()
 {
     if (function_exists('idn_to_utf8')) {
-        return function ($domain) {
-            return idn_to_utf8($domain, 0, INTL_IDNA_VARIANT_UTS46);
-        };
+        if (defined('INTL_IDNA_VARIANT_UTS46')) {
+            return function ($domain) {
+                return idn_to_utf8($domain, 0, INTL_IDNA_VARIANT_UTS46);
+            };
+        }
+        return 'idn_to_utf8';
     }
 
     $hostnameValidator = new Hostname();
diff --git a/src/EmailAddress.php b/src/EmailAddress.php
index bd58018dc..ab5e9db9b 100644
--- a/src/EmailAddress.php
+++ b/src/EmailAddress.php
@@ -554,7 +554,10 @@ public function isValid($value)
     protected function idnToAscii($email)
     {
         if (extension_loaded('intl')) {
-            return (idn_to_ascii($email, 0, INTL_IDNA_VARIANT_UTS46) ?: $email);
+            if (defined('INTL_IDNA_VARIANT_UTS46')) {
+                return (idn_to_ascii($email, 0, INTL_IDNA_VARIANT_UTS46) ?: $email);
+            }
+            return (idn_to_ascii($email) ?: $email);
         }
         return $email;
     }
@@ -577,7 +580,10 @@ protected function idnToUtf8($email)
             // the source string in those cases.
             // But not when the source string is long enough.
             // Thus we default to source string ourselves.
-            return idn_to_utf8($email, 0, INTL_IDNA_VARIANT_UTS46) ?: $email;
+            if (defined('INTL_IDNA_VARIANT_UTS46')) {
+                return idn_to_utf8($email, 0, INTL_IDNA_VARIANT_UTS46) ?: $email;
+            }
+            return idn_to_utf8($email) ?: $email;
         }
         return $email;
     }