diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index 6dc7c97..27d3e42 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -19,9 +19,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-version: ['8.3', '8.4', '8.5']
+        php-version: ['8.5', '8.6']
 
-    uses: simplesamlphp/simplesamlphp-test-framework/.github/workflows/reusable_phplinter.yml@v1
+    uses: simplesamlphp/simplesamlphp-test-framework/.github/workflows/reusable_phplinter.yml@v2
     secrets: inherit
     with:
       php-version: ${{ matrix.php-version }}
@@ -31,7 +31,7 @@ jobs:
     strategy:
       fail-fast: false
 
-    uses: simplesamlphp/simplesamlphp-test-framework/.github/workflows/reusable_linter.yml@v1
+    uses: simplesamlphp/simplesamlphp-test-framework/.github/workflows/reusable_linter.yml@v2
     secrets: inherit
     with:
       enable_eslinter: false
@@ -47,7 +47,7 @@ jobs:
       fail-fast: false
       matrix:
         operating-system: [ubuntu-latest]
-        php-versions: ['8.3', '8.4', '8.5']
+        php-versions: ['8.5', '8.6']
 
     steps:
       - name: Setup PHP, with composer and extensions
@@ -57,7 +57,7 @@ jobs:
           php-version: ${{ matrix.php-versions }}
           extensions: ctype, date, filter, intl, pcre, sodium, spl
           tools: composer
-          ini-values: error_reporting=E_ALL
+          ini-values: display_errors=on, error_reporting=E_ALL
           coverage: pcov
 
       - name: Setup problem matchers for PHP
@@ -109,7 +109,7 @@ jobs:
       fail-fast: true
       matrix:
         operating-system: [windows-latest]
-        php-versions: ['8.3', '8.4', '8.5']
+        php-versions: ['8.5']
 
     steps:
       - name: Setup PHP, with composer and extensions
@@ -218,7 +218,7 @@ jobs:
         uses: shivammathur/setup-php@v2
         with:
           # Should be the lowest supported version
-          php-version: '8.3'
+          php-version: '8.5'
           extensions: ctype, date, filter, pcre, sodium, spl
           tools: composer
           coverage: none
diff --git a/composer.json b/composer.json
index 7af6d4e..6920e3b 100644
--- a/composer.json
+++ b/composer.json
@@ -13,19 +13,19 @@
         }
     ],
     "require": {
-        "php": "^8.3",
+        "php": "^8.5",
         "ext-date": "*",
         "ext-filter": "*",
         "ext-pcre": "*",
         "ext-spl": "*",
+        "ext-uri": "*",
 
-        "guzzlehttp/psr7": "~2.8",
         "webmozart/assert": "~2.1"
     },
     "require-dev": {
         "ext-intl": "*",
 
-        "simplesamlphp/simplesamlphp-test-framework": "~1.11"
+        "simplesamlphp/simplesamlphp-test-framework": "~2"
     },
     "autoload": {
         "psr-4": {
@@ -40,7 +40,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "v2.1.x-dev"
+            "dev-master": "v3.0.x-dev"
         }
     },
     "config": {
diff --git a/src/URITrait.php b/src/URITrait.php
index 84fb2c9..383df83 100644
--- a/src/URITrait.php
+++ b/src/URITrait.php
@@ -4,9 +4,11 @@
 
 namespace SimpleSAML\Assert;
 
-use GuzzleHttp\Psr7\Exception\MalformedUriException;
-use GuzzleHttp\Psr7\Uri;
 use InvalidArgumentException;
+use Uri\InvalidUriException;
+use Uri\Rfc3986\Uri;
+use Uri\WhatWg\InvalidUrlException;
+use Uri\WhatWg\Url;
 
 use function sprintf;
 use function strlen;
@@ -25,7 +27,7 @@ trait URITrait
      *          not handle any custom exception passed to it.                          *
      ***********************************************************************************/
 
-    private static Uri $uri;
+    private static Uri|Url $uri;
 
 
     /**
@@ -34,7 +36,7 @@ protected static function validURN(string $value, string $message = ''): string
     {
         try {
             self::$uri = new Uri($value);
-        } catch (MalformedUriException $e) {
+        } catch (InvalidUriException $e) {
             throw new InvalidArgumentException(sprintf(
                 $message ?: '\'%s\' is not a valid RFC3986 compliant URI',
                 $value,
@@ -60,17 +62,17 @@ protected static function validURN(string $value, string $message = ''): string
     protected static function validURL(string $value, string $message = ''): string
     {
         try {
-            self::$uri = new Uri($value);
-        } catch (MalformedUriException $e) {
+            self::$uri = new Url($value);
+        } catch (InvalidUrlException $e) {
             throw new InvalidArgumentException(sprintf(
-                $message ?: '\'%s\' is not a valid RFC3986 compliant URI',
+                $message ?: '\'%s\' is not a valid WhatWg compliant URI',
                 $value,
             ));
         }
 
         if (self::$uri->getScheme() !== 'http' && self::$uri->getScheme() !== 'https') {
             throw new InvalidArgumentException(sprintf(
-                $message ?: '\'%s\' is not a valid RFC2396 compliant URL',
+                $message ?: '\'%s\' is not a valid WhatWg compliant URL',
                 $value,
             ));
         }
@@ -83,13 +85,31 @@ protected static function validURL(string $value, string $message = ''): string
      */
     protected static function validURI(string $value, string $message = ''): string
     {
+        $failure = false;
         try {
             self::$uri = new Uri($value);
-        } catch (MalformedUriException $e) {
-            throw new InvalidArgumentException(sprintf(
-                $message ?: '\'%s\' is not a valid RFC3986 compliant URI',
-                $value,
-            ));
+        } catch (InvalidUriException $e) {
+            $failure = true;
+        }
+
+        if ($failure === true) {
+            try {
+                self::$uri = new Url($value);
+            } catch (InvalidUrlException $e) {
+                throw new InvalidArgumentException(sprintf(
+                    $message ?: '\'%s\' is not a valid WhatWg compliant URL',
+                    $value,
+                ));
+            } finally {
+                $failure = false;
+            }
+
+            if ($failure === true) {
+                throw new InvalidArgumentException(sprintf(
+                    $message ?: '\'%s\' is not a valid RFC3986 compliant URI',
+                    $value,
+                ));
+            }
         }
 
         return $value;
diff --git a/tests/Assert/AssertTest.php b/tests/Assert/AssertTest.php
index aebd747..7c79957 100644
--- a/tests/Assert/AssertTest.php
+++ b/tests/Assert/AssertTest.php
@@ -125,7 +125,6 @@ public function testValueToString(mixed $value, string $expected): void
     {
         $assert = new Assert();
         $method = new ReflectionMethod(Assert::class, 'valueToString');
-        $method->setAccessible(true);
 
         $this->assertEquals($expected, $method->invoke($assert, $value));
     }
diff --git a/tests/Assert/URITest.php b/tests/Assert/URITest.php
index e9317a4..a9c7f10 100644
--- a/tests/Assert/URITest.php
+++ b/tests/Assert/URITest.php
@@ -79,9 +79,9 @@ public static function provideURI(): array
             'intl' => [true, 'https://niño.com'],
             'spn' => [true, 'spn:a4cf592f-a64c-46ff-a788-b260f474525b'],
             'typos' => [true, 'https//www.uni.l/en/'],
-            'spaces' => [true, 'this is silly'],
+            'spaces' => [false, 'this is silly'],
             'empty' => [true, ''],
-            'azure-common' => [true, 'https://sts.windows.net/{tenantid}/'],
+            'azure-common' => [true, 'https://sts.windows.net/123e4567-e89b-12d3-a456-426614174000/'],
             'email' => [true, 'scoobydoo@whereareyou.org'],
         ];
     }