diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index 8bb4293..12ce07f 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -212,7 +212,7 @@ jobs:
         uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php-versions }}
-          extensions: ctype, date, filter, pcre, spl
+          extensions: ctype, date, filter, intl, pcre, spl
           tools: composer
           ini-values: error_reporting=E_ALL
           coverage: none
diff --git a/composer.json b/composer.json
index 14474cd..aa5ae8a 100644
--- a/composer.json
+++ b/composer.json
@@ -19,10 +19,11 @@
         "ext-pcre": "*",
         "ext-spl": "*",
 
+        "league/uri-interfaces": "^7.4",
         "webmozart/assert": "^1.11"
     },
     "require-dev": {
-        "simplesamlphp/simplesamlphp-test-framework": "^1.5.5"
+        "simplesamlphp/simplesamlphp-test-framework": "^1.7"
     },
     "autoload": {
         "psr-4": {
@@ -44,7 +45,8 @@
         "allow-plugins": {
             "composer/package-versions-deprecated": true,
             "dealerdirect/phpcodesniffer-composer-installer": true,
-            "simplesamlphp/composer-module-installer": false
+            "simplesamlphp/composer-module-installer": false,
+            "phpstan/extension-installer": true
         }
     }
 }
diff --git a/src/CustomAssertionTrait.php b/src/CustomAssertionTrait.php
index 8b37917..7d67ce3 100644
--- a/src/CustomAssertionTrait.php
+++ b/src/CustomAssertionTrait.php
@@ -4,9 +4,9 @@
 
 namespace SimpleSAML\Assert;
 
-use DateTimeImmutable; // Requires ext-date
-use DateTimeInterface; // Requires ext-date
 use InvalidArgumentException;
+use League\Uri\Exceptions\SyntaxError;
+use League\Uri\UriString;
 
 use function array_map;
 use function base64_decode;
@@ -37,15 +37,6 @@ trait CustomAssertionTrait
     /** @var string */
     private static string $base64_regex = '/^(?:[a-z0-9+\/]{4})*(?:[a-z0-9+\/]{2}==|[a-z0-9+\/]{3}=)?$/i';
 
-    /** @var string */
-    private static string $uri_same_document_regex = '#^(?:\#([A-Za-z][A-Za-z0-9+\-.]*:(?:\/\/(?:(?:[A-Za-z0-9\-._~!$&\'()*+,;=:]|%[0-9A-Fa-f]{2})*@)?(?:\[(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){6}|::(?:[0-9A-Fa-f]{1,4}:){5}|(?:[0-9A-Fa-f]{1,4})?::(?:[0-9A-Fa-f]{1,4}:){4}|(?:(?:[0-9A-Fa-f]{1,4}:){0,1}[0-9A-Fa-f]{1,4})?::(?:[0-9A-Fa-f]{1,4}:){3}|(?:(?:[0-9A-Fa-f]{1,4}:){0,2}[0-9A-Fa-f]{1,4})?::(?:[0-9A-Fa-f]{1,4}:){2}|(?:(?:[0-9A-Fa-f]{1,4}:){0,3}[0-9A-Fa-f]{1,4})?::[0-9A-Fa-f]{1,4}:|(?:(?:[0-9A-Fa-f]{1,4}:){0,4}[0-9A-Fa-f]{1,4})?::)(?:[0-9A-Fa-f]{1,4}:[0-9A-Fa-f]{1,4}|(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))|(?:(?:[0-9A-Fa-f]{1,4}:){0,5}[0-9A-Fa-f]{1,4})?::[0-9A-Fa-f]{1,4}|(?:(?:[0-9A-Fa-f]{1,4}:){0,6}[0-9A-Fa-f]{1,4})?::)|[Vv][0-9A-Fa-f]+\.[A-Za-z0-9\-._~!$&\'()*+,;=:]+)\]|(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)|(?:[A-Za-z0-9\-._~!$&\'()*+,;=]|%[0-9A-Fa-f]{2})*)(?::[0-9]*)?(?:\/(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})*)*|\/(?:(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})+(?:\/(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})*)*)?|(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})+(?:\/(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})*)*|)(?:\?(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@/?]|%[0-9A-Fa-f]{2})*)?(?:\#(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@/?]|%[0-9A-Fa-f]{2})*)?|(?:\/\/(?:(?:[A-Za-z0-9\-._~!$&\'()*+,;=:]|%[0-9A-Fa-f]{2})*@)?(?:\[(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){6}|::(?:[0-9A-Fa-f]{1,4}:){5}|(?:[0-9A-Fa-f]{1,4})?::(?:[0-9A-Fa-f]{1,4}:){4}|(?:(?:[0-9A-Fa-f]{1,4}:){0,1}[0-9A-Fa-f]{1,4})?::(?:[0-9A-Fa-f]{1,4}:){3}|(?:(?:[0-9A-Fa-f]{1,4}:){0,2}[0-9A-Fa-f]{1,4})?::(?:[0-9A-Fa-f]{1,4}:){2}|(?:(?:[0-9A-Fa-f]{1,4}:){0,3}[0-9A-Fa-f]{1,4})?::[0-9A-Fa-f]{1,4}:|(?:(?:[0-9A-Fa-f]{1,4}:){0,4}[0-9A-Fa-f]{1,4})?::)(?:[0-9A-Fa-f]{1,4}:[0-9A-Fa-f]{1,4}|(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))|(?:(?:[0-9A-Fa-f]{1,4}:){0,5}[0-9A-Fa-f]{1,4})?::[0-9A-Fa-f]{1,4}|(?:(?:[0-9A-Fa-f]{1,4}:){0,6}[0-9A-Fa-f]{1,4})?::)|[Vv][0-9A-Fa-f]+\.[A-Za-z0-9\-._~!$&\'()*+,;=:]+)\]|(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)|(?:[A-Za-z0-9\-._~!$&\'()*+,;=]|%[0-9A-Fa-f]{2})*)(?::[0-9]*)?(?:\/(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})*)*|\/(?:(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})+(?:\/(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})*)*)?|(?:[A-Za-z0-9\-._~!$&\'()*+,;=@]|%[0-9A-Fa-f]{2})+(?:\/(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})*)*|)(?:\?(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@/?]|%[0-9A-Fa-f]{2})*)?(?:\#(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@/?]|%[0-9A-Fa-f]{2})*)?))$#';
-
-    /** @var string */
-    private static string $urn_regex = '/\A(?i:urn:(?!urn:)(?<nid>[a-z0-9][a-z0-9-]{1,31}):(?<nss>(?:[-a-z0-9()+,.:=@;$_!*\'&~\/]|%[0-9a-f]{2})+)(?:\?\+(?<rcomponent>.*?))?(?:\?=(?<qcomponent>.*?))?(?:#(?<fcomponent>.*?))?)\z/';
-
-    /** @var string */
-    private static string $uri_regex = '#[A-Za-z][A-Za-z0-9+\-.]*:(?:\/\/(?:(?:[A-Za-z0-9\-._~!$&\'()*+,;=:]|%[0-9A-Fa-f]{2})*@)?(?:\[(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){6}|::(?:[0-9A-Fa-f]{1,4}:){5}|(?:[0-9A-Fa-f]{1,4})?::(?:[0-9A-Fa-f]{1,4}:){4}|(?:(?:[0-9A-Fa-f]{1,4}:){0,1}[0-9A-Fa-f]{1,4})?::(?:[0-9A-Fa-f]{1,4}:){3}|(?:(?:[0-9A-Fa-f]{1,4}:){0,2}[0-9A-Fa-f]{1,4})?::(?:[0-9A-Fa-f]{1,4}:){2}|(?:(?:[0-9A-Fa-f]{1,4}:){0,3}[0-9A-Fa-f]{1,4})?::[0-9A-Fa-f]{1,4}:|(?:(?:[0-9A-Fa-f]{1,4}:){0,4}[0-9A-Fa-f]{1,4})?::)(?:[0-9A-Fa-f]{1,4}:[0-9A-Fa-f]{1,4}|(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))|(?:(?:[0-9A-Fa-f]{1,4}:){0,5}[0-9A-Fa-f]{1,4})?::[0-9A-Fa-f]{1,4}|(?:(?:[0-9A-Fa-f]{1,4}:){0,6}[0-9A-Fa-f]{1,4})?::)|[Vv][0-9A-Fa-f]+\.[A-Za-z0-9\-._~!$&\'()*+,;=:]+)\]|(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)|(?:[A-Za-z0-9\-._~!$&\'()*+,;=]|%[0-9A-Fa-f]{2})*)(?::[0-9]*)?(?:\/(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})*)*|\/(?:(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})+(?:\/(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})*)*)?|(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})+(?:\/(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})*)*|)(?:\?(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@/?]|%[0-9A-Fa-f]{2})*)?(?:\#(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@/?]|%[0-9A-Fa-f]{2})*)?#';
-
     /** @var string */
     private static string $hostname_regex = '/^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])$/';
 
@@ -168,7 +159,19 @@ private static function notInArray($value, array $values, string $message = ''):
      */
     private static function validURN(string $value, string $message = ''): void
     {
-        if (filter_var($value, FILTER_VALIDATE_REGEXP, ['options' => ['regexp' => self::$urn_regex]]) === false) {
+        try {
+            $uri = UriString::parse($value);
+        } catch (SyntaxError $e) {
+            throw new InvalidArgumentException(sprintf(
+                $message ?: '\'%s\' is not a valid RFC3986 compliant URI',
+                $value,
+            ));
+        }
+
+        if (
+            $uri['scheme'] !== 'urn'
+            || (($uri['scheme'] !== null) && $uri['path'] !== substr($value, strlen($uri['scheme']) + 1))
+        ) {
             throw new InvalidArgumentException(sprintf(
                 $message ?: '\'%s\' is not a valid RFC8141 compliant URN',
                 $value,
@@ -183,7 +186,16 @@ private static function validURN(string $value, string $message = ''): void
      */
     private static function validURL(string $value, string $message = ''): void
     {
-        if (filter_var($value, FILTER_VALIDATE_URL) === false) {
+        try {
+            $uri = UriString::parse($value);
+        } catch (SyntaxError $e) {
+            throw new InvalidArgumentException(sprintf(
+                $message ?: '\'%s\' is not a valid RFC3986 compliant URI',
+                $value,
+            ));
+        }
+
+        if ($uri['scheme'] !== 'http' && $uri['scheme'] !== 'https') {
             throw new InvalidArgumentException(sprintf(
                 $message ?: '\'%s\' is not a valid RFC2396 compliant URL',
                 $value,
@@ -198,12 +210,9 @@ private static function validURL(string $value, string $message = ''): void
      */
     private static function validURI(string $value, string $message = ''): void
     {
-        if (
-            filter_var($value, FILTER_VALIDATE_REGEXP, ['options' => ['regexp' => self::$uri_regex]]) === false &&
-            // We're very lenient here to accept DNS hostnames without a scheme
-            filter_var($value, FILTER_VALIDATE_REGEXP, ['options' => ['regexp' => self::$hostname_regex]]) === false &&
-            filter_var($value, FILTER_VALIDATE_REGEXP, ['options' => ['regexp' => self::$uri_same_document_regex]]) === false
-        ) {
+        try {
+            UriString::parse($value);
+        } catch (SyntaxError $e) {
             throw new InvalidArgumentException(sprintf(
                 $message ?: '\'%s\' is not a valid RFC3986 compliant URI',
                 $value,
diff --git a/tests/Assert/URITest.php b/tests/Assert/URITest.php
index 85391f0..83d64cd 100644
--- a/tests/Assert/URITest.php
+++ b/tests/Assert/URITest.php
@@ -75,8 +75,10 @@ public static function provideURI(): array
             'urn' => [true, 'urn:x-simplesamlphp:phpunit'],
             'same-doc' => [true, '#_53d830ab1be17291a546c95c7f1cdf8d3d23c959e6'],
             'url' => [true, 'https://www.simplesamlphp.org'],
-            'bogus' => [false, 'stupid value'],
+            'invalid_char' => [false, 'https://a⒈com'],
+            'intl' => [true, 'https://niño.com'],
             'spn' => [true, 'spn:a4cf592f-a64c-46ff-a788-b260f474525b'],
+            'typos' => [true, 'https//www.uni.l/en/'],
         ];
     }
 
@@ -90,8 +92,10 @@ public static function provideURL(): array
             'url' => [true, 'https://www.simplesamlphp.org'],
             'same-doc' => [false, '#_53d830ab1be17291a546c95c7f1cdf8d3d23c959e6'],
             'urn' => [false, 'urn:x-simplesamlphp:phpunit'],
-            'bogus' => [false, 'stupid value'],
+            'invalid_char' => [false, 'https://a⒈com'],
+            'intl' => [true, 'https://niño.com'],
             'spn' => [false, 'spn:a4cf592f-a64c-46ff-a788-b260f474525b'],
+            'typos' => [false, 'https//www.uni.l/en/'],
         ];
     }
 
@@ -105,8 +109,10 @@ public static function provideURN(): array
             'urn' => [true, 'urn:x-simplesamlphp:phpunit'],
             'url' => [false, 'https://www.simplesamlphp.org'],
             'same-doc' => [false, '#_53d830ab1be17291a546c95c7f1cdf8d3d23c959e6'],
-            'bogus' => [false, 'stupid value'],
+            'invalid_char' => [false, 'https://a⒈com'],
+            'intl' => [false, 'https://niño.com'],
             'spn' => [false, 'spn:a4cf592f-a64c-46ff-a788-b260f474525b'],
+            'typos' => [false, 'https//www.uni.l/en/'],
         ];
     }
 }