diff --git a/.gitattributes b/.gitattributes
index 385679d..64f9589 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,5 +1,4 @@
 /dev-tools/         export-ignore
 /tests/             export-ignore
 /.*                 export-ignore
-/phpmd.xml          export-ignore
 /phpunit.xml.dist   export-ignore
diff --git a/.travis.yml b/.travis.yml
index ba85c50..a096263 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -15,7 +15,8 @@ php:
     - 7.1
     - 7.2
     - 7.3
-    - 7.4snapshot
+    - 7.4
+    - nightly
 
 env:
     global:
@@ -44,7 +45,7 @@ jobs:
     include:
         -
             stage: Static code analysis
-            php: 7.3
+            php: 7.4
             install:
                 - travis_retry composer update $DEFAULT_COMPOSER_FLAGS
                 - travis_retry composer update -d dev-tools $DEFAULT_COMPOSER_FLAGS
@@ -52,6 +53,5 @@ jobs:
             script:
                 - composer validate --strict || travis_terminate 1
                 - composer normalize -d ./dev-tools ./../composer.json --dry-run || travis_terminate 1
-                - dev-tools/vendor/bin/composer-require-checker check composer.json --config-file=.composer-require-checker.json || travis_terminate 1
-                - dev-tools/vendor/bin/phpmd src,tests text phpmd.xml || travis_terminate 1
+                - dev-tools/vendor/bin/phpmd src,tests text ./dev-tools/phpmd.xml || travis_terminate 1
                 - dev-tools/vendor/bin/php-cs-fixer fix --diff --dry-run -v || travis_terminate 1
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..a469cd4
--- /dev/null
+++ b/README.md
@@ -0,0 +1,8 @@
+# PHP-CS-Fixer/phpunit-constraint-xmlmatchesxsd
+
+This version is for [PHP CS Fixer](https://github.com/FriendsOfPHP/PHP-CS-Fixer) only! Do not use it!
+
+We hope to see this assert to be provided by PHPUnit itself,
+please help out if you can to make this happen.
+
+For questions visit us @ https://gitter.im/PHP-CS-Fixer/Lobby
diff --git a/composer.json b/composer.json
index 02b05ad..b0b86d4 100644
--- a/composer.json
+++ b/composer.json
@@ -13,11 +13,10 @@
         }
     ],
     "require": {
-        "php": "^5.5 || ^7.0",
+        "php": "^5.5 || ^7.0 || ^8.0",
         "ext-dom": "*",
         "ext-libxml": "*",
-        "phpunit/phpunit": "^5.7.23 || ^6.4.3 || ^7.0 || ^8.0",
-        "phpunitgoodpractices/polyfill": "^1.1"
+        "phpunit/phpunit": "^5.7.23 || ^6.4.3 || ^7.0 || ^8.0 || ^9.0"
     },
     "conflict": {
         "hhvm": "*"
diff --git a/dev-tools/composer.json b/dev-tools/composer.json
index c12a204..b3edbb0 100644
--- a/dev-tools/composer.json
+++ b/dev-tools/composer.json
@@ -1,14 +1,13 @@
 {
     "require": {
-        "php": "^7.3"
+        "php": "^7.3 || ^8.0"
     },
     "conflict": {
         "hhvm": "*"
     },
     "require-dev": {
-        "friendsofphp/php-cs-fixer": "^2.14",
-        "localheinz/composer-normalize": "^1.1",
-        "maglnet/composer-require-checker": "^2.0",
+        "friendsofphp/php-cs-fixer": "^2.15",
+        "ergebnis/composer-normalize": "^2.5.1",
         "mi-schi/phpmd-extension": "^4.3",
         "phpmd/phpmd": "^2.6"
     },
diff --git a/phpmd.xml b/dev-tools/phpmd.xml
similarity index 100%
rename from phpmd.xml
rename to dev-tools/phpmd.xml
diff --git a/src/Constraint/XmlMatchesXsdForV5.php b/src/Constraint/XmlMatchesXsdForV5.php
index 5853942..b2be1b9 100644
--- a/src/Constraint/XmlMatchesXsdForV5.php
+++ b/src/Constraint/XmlMatchesXsdForV5.php
@@ -98,7 +98,6 @@ protected function matches($other)
     private function stringMatches($other)
     {
         $internalErrors = libxml_use_internal_errors(true);
-        $disableEntities = libxml_disable_entity_loader(true);
         libxml_clear_errors();
 
         $dom = new \DOMDocument();
@@ -106,7 +105,6 @@ private function stringMatches($other)
         $dom->validateOnParse = true;
 
         if (!@$dom->loadXML($other, LIBXML_NONET | (\defined('LIBXML_COMPACT') ? LIBXML_COMPACT : 0))) {
-            libxml_disable_entity_loader($disableEntities);
             $this->setXMLConstraintErrors();
             libxml_clear_errors();
             libxml_use_internal_errors($internalErrors);
@@ -116,7 +114,6 @@ private function stringMatches($other)
 
         $dom->normalizeDocument();
 
-        libxml_disable_entity_loader($disableEntities);
         libxml_clear_errors();
 
         if (false === $result = @$dom->schemaValidateSource($this->xsd)) {
diff --git a/src/Constraint/XmlMatchesXsdForV7.php b/src/Constraint/XmlMatchesXsdForV7.php
index 23f8587..822e656 100644
--- a/src/Constraint/XmlMatchesXsdForV7.php
+++ b/src/Constraint/XmlMatchesXsdForV7.php
@@ -94,7 +94,6 @@ protected function matches($other): bool
     private function stringMatches($other)
     {
         $internalErrors = libxml_use_internal_errors(true);
-        $disableEntities = libxml_disable_entity_loader(true);
         libxml_clear_errors();
 
         $dom = new \DOMDocument();
@@ -102,7 +101,6 @@ private function stringMatches($other)
         $dom->validateOnParse = true;
 
         if (!@$dom->loadXML($other, LIBXML_NONET | (\defined('LIBXML_COMPACT') ? LIBXML_COMPACT : 0))) {
-            libxml_disable_entity_loader($disableEntities);
             $this->setXMLConstraintErrors();
             libxml_clear_errors();
             libxml_use_internal_errors($internalErrors);
@@ -112,7 +110,6 @@ private function stringMatches($other)
 
         $dom->normalizeDocument();
 
-        libxml_disable_entity_loader($disableEntities);
         libxml_clear_errors();
 
         if (false === $result = @$dom->schemaValidateSource($this->xsd)) {
diff --git a/src/Constraint/XmlMatchesXsdForV8.php b/src/Constraint/XmlMatchesXsdForV8.php
index 6e1b906..fac5ba8 100644
--- a/src/Constraint/XmlMatchesXsdForV8.php
+++ b/src/Constraint/XmlMatchesXsdForV8.php
@@ -92,7 +92,6 @@ protected function matches($other): bool
     private function stringMatches($other)
     {
         $internalErrors = libxml_use_internal_errors(true);
-        $disableEntities = libxml_disable_entity_loader(true);
         libxml_clear_errors();
 
         $dom = new \DOMDocument();
@@ -100,7 +99,6 @@ private function stringMatches($other)
         $dom->validateOnParse = true;
 
         if (!@$dom->loadXML($other, LIBXML_NONET | (\defined('LIBXML_COMPACT') ? LIBXML_COMPACT : 0))) {
-            libxml_disable_entity_loader($disableEntities);
             $this->setXMLConstraintErrors();
             libxml_clear_errors();
             libxml_use_internal_errors($internalErrors);
@@ -110,7 +108,6 @@ private function stringMatches($other)
 
         $dom->normalizeDocument();
 
-        libxml_disable_entity_loader($disableEntities);
         libxml_clear_errors();
 
         if (false === $result = @$dom->schemaValidateSource($this->xsd)) {
diff --git a/tests/Constraint/XmlMatchesXsdTest.php b/tests/Constraint/XmlMatchesXsdTest.php
index ce8e1ec..23ca9be 100644
--- a/tests/Constraint/XmlMatchesXsdTest.php
+++ b/tests/Constraint/XmlMatchesXsdTest.php
@@ -39,14 +39,14 @@ public function testAssertXMLMatchesXSD()
         }
 
         $constraint->evaluate($content); // should not throw an exception
-        $this->assertTrue($constraint->evaluate($content, '', true));
+        static::assertTrue($constraint->evaluate($content, '', true));
     }
 
     public function testXMLValidConstraintBasics()
     {
         $constraint = new XmlMatchesXsd('');
-        $this->assertSame(1, $constraint->count());
-        $this->assertSame('matches XSD', $constraint->toString());
+        static::assertSame(1, $constraint->count());
+        static::assertSame('matches XSD', $constraint->toString());
     }
 
     public function testXMLValidConstraintFalse()
@@ -54,7 +54,7 @@ public function testXMLValidConstraintFalse()
         $this->expectException(
             'PHPUnit\Framework\ExpectationFailedException'
         );
-        $this->expectExceptionMessageRegExp(
+        $this->expectExceptionMessageRegex(
             '#^Failed asserting that boolean\# matches XSD\.$#'
         );
 
@@ -67,7 +67,7 @@ public function testXMLValidConstraintInt()
         $this->expectException(
             'PHPUnit\Framework\ExpectationFailedException'
         );
-        $this->expectExceptionMessageRegExp(
+        $this->expectExceptionMessageRegex(
             '#^Failed asserting that integer\#1 matches XSD\.$#'
         );
 
@@ -80,7 +80,7 @@ public function testXMLValidConstraintInvalidXML()
         $this->expectException(
             'PHPUnit\Framework\ExpectationFailedException'
         );
-        $this->expectExceptionMessageRegExp(
+        $this->expectExceptionMessageRegex(
             '#^Failed asserting that <a></b> matches XSD.[\n]\[error \d{1,}\](?s).*\.$#'
         );
 
@@ -93,7 +93,7 @@ public function testXMLValidConstraintNotMatchingXML()
         $this->expectException(
             'PHPUnit\Framework\ExpectationFailedException'
         );
-        $this->expectExceptionMessageRegExp(
+        $this->expectExceptionMessageRegex(
             '#^Failed asserting that <a></a> matches XSD.[\n]\[error \d{1,}\](?s).*\.$#'
         );
 
@@ -106,7 +106,7 @@ public function testXMLValidConstraintNull()
         $this->expectException(
             'PHPUnit\Framework\ExpectationFailedException'
         );
-        $this->expectExceptionMessageRegExp(
+        $this->expectExceptionMessageRegex(
             '#^Failed asserting that null matches XSD\.$#'
         );
 
@@ -119,7 +119,7 @@ public function testXMLValidConstraintObject()
         $this->expectException(
             'PHPUnit\Framework\ExpectationFailedException'
         );
-        $this->expectExceptionMessageRegExp(
+        $this->expectExceptionMessageRegex(
             '#^Failed asserting that stdClass\# matches XSD\.$#'
         );
 
@@ -142,4 +142,18 @@ private function getAssetsDir()
     {
         return __DIR__.'/../Fixtures/XmlMatchesXsdTest/';
     }
+
+    /**
+     * @param string $pattern
+     */
+    private function expectExceptionMessageRegex($pattern)
+    {
+        if (method_exists($this, 'expectExceptionMessageRegExp')) {
+            $this->expectExceptionMessageRegExp($pattern);
+        } elseif (method_exists($this, 'expectDeprecationMessageMatches')) {
+            $this->expectDeprecationMessageMatches($pattern);
+        } else {
+            throw new \RuntimeException('Unknown how to match against exception message.');
+        }
+    }
 }