diff --git a/core/modules/link/src/Plugin/migrate/process/d6/FieldLink.php b/core/modules/link/src/Plugin/migrate/process/d6/FieldLink.php
index aaede46..5447385 100644
--- a/core/modules/link/src/Plugin/migrate/process/d6/FieldLink.php
+++ b/core/modules/link/src/Plugin/migrate/process/d6/FieldLink.php
@@ -58,86 +58,28 @@ protected function canonicalizeUri($uri) {
       $uri = substr($uri, strlen('<front>'));
     }
     else {
-      // @TODO Complete letters.
-      $LINK_ICHARS_DOMAIN = (string) html_entity_decode(implode("", [
-        "&#x00E6;", // æ
-        "&#x00C6;", // Æ
-        "&#x00C0;", // À
-        "&#x00E0;", // à
-        "&#x00C1;", // Á
-        "&#x00E1;", // á
-        "&#x00C2;", // Â
-        "&#x00E2;", // â
-        "&#x00E5;", // å
-        "&#x00C5;", // Å
-        "&#x00E4;", // ä
-        "&#x00C4;", // Ä
-        "&#x00C7;", // Ç
-        "&#x00E7;", // ç
-        "&#x00D0;", // Ð
-        "&#x00F0;", // ð
-        "&#x00C8;", // È
-        "&#x00E8;", // è
-        "&#x00C9;", // É
-        "&#x00E9;", // é
-        "&#x00CA;", // Ê
-        "&#x00EA;", // ê
-        "&#x00CB;", // Ë
-        "&#x00EB;", // ë
-        "&#x00CE;", // Î
-        "&#x00EE;", // î
-        "&#x00CF;", // Ï
-        "&#x00EF;", // ï
-        "&#x00F8;", // ø
-        "&#x00D8;", // Ø
-        "&#x00F6;", // ö
-        "&#x00D6;", // Ö
-        "&#x00D4;", // Ô
-        "&#x00F4;", // ô
-        "&#x00D5;", // Õ
-        "&#x00F5;", // õ
-        "&#x0152;", // Œ
-        "&#x0153;", // œ
-        "&#x00FC;", // ü
-        "&#x00DC;", // Ü
-        "&#x00D9;", // Ù
-        "&#x00F9;", // ù
-        "&#x00DB;", // Û
-        "&#x00FB;", // û
-        "&#x0178;", // Ÿ
-        "&#x00FF;", // ÿ
-        "&#x00D1;", // Ñ
-        "&#x00F1;", // ñ
-        "&#x00FE;", // þ
-        "&#x00DE;", // Þ
-        "&#x00FD;", // ý
-        "&#x00DD;", // Ý
-        "&#x00BF;", // ¿
-      ]), ENT_QUOTES, 'UTF-8');
-
-      $LINK_ICHARS = $LINK_ICHARS_DOMAIN . (string) html_entity_decode(implode("", [
-          "&#x00DF;", // ß
-        ]), ENT_QUOTES, 'UTF-8');
+      // A list of unicode-encoded characters that could be included in a uri.
+      $link_ichars = '¡¢£¤¥¦§¨©ª«¬­®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿŒœŠšŸŽžƒ';
 
       // Pattern specific to internal links.
-      $internal_pattern = "/^(?:[a-z0-9" . $LINK_ICHARS . "_\-+\[\] ]+)";
+      $internal_pattern = "/^(?:[a-z0-9" . $link_ichars . "_\-+\[\] ]+)";
 
-      $directories = "(?:\/[a-z0-9" . $LINK_ICHARS . "_\-\.~+%=&,$'#!():;*@\[\]]*)*";
+      $directories = "(?:\/[a-z0-9" . $link_ichars . "_\-\.~+%=&,$'#!():;*@\[\]]*)*";
       // Yes, four backslashes == a single backslash.
-      $query = "(?:\/?\?([?a-z0-9" . $LINK_ICHARS . "+_|\-\.~\/\\\\%=&,$'():;*@\[\]{} ]*))";
-      $anchor = "(?:#[a-z0-9" . $LINK_ICHARS . "_\-\.~+%=&,$'():;*@\[\]\/\?]*)";
+      $query = "(?:\/?\?([?a-z0-9" . $link_ichars . "+_|\-\.~\/\\\\%=&,$'():;*@\[\]{} ]*))";
+      $anchor = "(?:#[a-z0-9" . $link_ichars . "_\-\.~+%=&,$'():;*@\[\]\/\?]*)";
 
       // The rest of the path for a standard URL.
       $end = $directories . '?' . $query . '?' . $anchor . '?' . '$/i';
 
       if (!preg_match($internal_pattern . $end, $uri)) {
         $allowed_protocols = ['http', 'https', 'ftp', 'news', 'nntp', 'telnet', 'mailto', 'irc', 'ssh', 'sftp', 'webcal'];
-        $LINK_DOMAINS = 'aero|arpa|asia|biz|com|cat|coop|edu|gov|info|int|jobs|mil|museum|name|nato|net|org|pro|travel|mobi|local';
+        $link_domains = 'aero|arpa|asia|biz|com|cat|coop|edu|gov|info|int|jobs|mil|museum|name|nato|net|org|pro|travel|mobi|local';
 
         // Starting a parenthesis group with (?: means that it is grouped, but is not captured
         $protocol = '((?:' . implode("|", $allowed_protocols) . '):\/\/)';
-        $authentication = "(?:(?:(?:[\w\.\-\+!$&'\(\)*\+,;=" . $LINK_ICHARS . "]|%[0-9a-f]{2})+(?::(?:[\w" . $LINK_ICHARS . "\.\-\+%!$&'\(\)*\+,;=]|%[0-9a-f]{2})*)?)?@)";
-        $domain = '(?:(?:[a-z0-9' . $LINK_ICHARS_DOMAIN . ']([a-z0-9' . $LINK_ICHARS_DOMAIN . '\-_\[\]])*)(\.(([a-z0-9' . $LINK_ICHARS_DOMAIN . '\-_\[\]])+\.)*(' . $LINK_DOMAINS . '|[a-z]{2}))?)';
+        $authentication = "(?:(?:(?:[\w\.\-\+!$&'\(\)*\+,;=" . $link_ichars . "]|%[0-9a-f]{2})+(?::(?:[\w" . $link_ichars . "\.\-\+%!$&'\(\)*\+,;=]|%[0-9a-f]{2})*)?)?@)";
+        $domain = '(?:(?:[a-z0-9' . $link_ichars . ']([a-z0-9' . $link_ichars . '\-_\[\]])*)(\.(([a-z0-9' . $link_ichars . '\-_\[\]])+\.)*(' . $link_domains . '|[a-z]{2}))?)';
         $ipv4 = '(?:[0-9]{1,3}(\.[0-9]{1,3}){3})';
         $ipv6 = '(?:[0-9a-fA-F]{1,4}(\:[0-9a-fA-F]{1,4}){7})';
         $port = '(?::([0-9]{1,5}))';
diff --git a/core/modules/link/tests/src/Unit/Plugin/migrate/process/d6/FieldLinkTest.php b/core/modules/link/tests/src/Unit/Plugin/migrate/process/d6/FieldLinkTest.php
index 5815390..55f72ca 100644
--- a/core/modules/link/tests/src/Unit/Plugin/migrate/process/d6/FieldLinkTest.php
+++ b/core/modules/link/tests/src/Unit/Plugin/migrate/process/d6/FieldLinkTest.php
@@ -62,6 +62,10 @@ public function canonicalizeUriDataProvider() {
         'yahoo.com',
         'http://yahoo.com',
       ],
+      'Absolute URL with non-standard characters' => [
+        'http://www.ßÀÑÐ¥ƒå¢ë.com',
+        'http://www.ßÀÑÐ¥ƒå¢ë.com',
+      ],
     ];
   }