diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 05134d6..43e3b8d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -32,6 +32,7 @@ jobs:
         with:
           php-version: ${{ matrix.php }}
           coverage: xdebug
+          ini-file: development
       - run: composer install
       - run: vendor/bin/phpunit --coverage-text
         if: ${{ matrix.php >= 7.3 }}
@@ -57,7 +58,7 @@ jobs:
     continue-on-error: true
     steps:
       - uses: actions/checkout@v3
-      - run: cp `which composer` composer.phar && ./composer.phar self-update --2.2 # downgrade Composer for HHVM
+      - run: cp "$(which composer)" composer.phar && ./composer.phar self-update --2.2 # downgrade Composer for HHVM
       - name: Run hhvm composer.phar install
         uses: docker://hhvm/hhvm:3.30-lts-latest
         with:
diff --git a/composer.json b/composer.json
index ae325fc..8613aa9 100644
--- a/composer.json
+++ b/composer.json
@@ -35,7 +35,7 @@
         "react/stream": "^1.2"
     },
     "require-dev": {
-        "phpunit/phpunit": "^9.3 || ^5.7 || ^4.8.35",
+        "phpunit/phpunit": "^9.5 || ^5.7 || ^4.8.35",
         "react/async": "^4 || ^3 || ^2",
         "react/promise-stream": "^1.4"
     },
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 93a36f6..7a9577e 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<!-- PHPUnit configuration file with new format for PHPUnit 9.3+ -->
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
-         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd"
+<!-- PHPUnit configuration file with new format for PHPUnit 9.5+ -->
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.5/phpunit.xsd"
          bootstrap="vendor/autoload.php"
          cacheResult="false"
          colors="true"
@@ -17,4 +17,12 @@
             <directory>./src/</directory>
         </include>
     </coverage>
+    <php>
+        <ini name="error_reporting" value="-1" />
+        <!-- Evaluate assertions, requires running with "php -d zend.assertions=1 vendor/bin/phpunit" -->
+        <!-- <ini name="zend.assertions=1" value="1" /> -->
+        <ini name="assert.active" value="1" />
+        <ini name="assert.exception" value="1" />
+        <ini name="assert.bail" value="0" />
+    </php>
 </phpunit>
diff --git a/phpunit.xml.legacy b/phpunit.xml.legacy
index fbb43e8..0d35225 100644
--- a/phpunit.xml.legacy
+++ b/phpunit.xml.legacy
@@ -15,4 +15,12 @@
             <directory>./src/</directory>
         </whitelist>
     </filter>
+    <php>
+        <ini name="error_reporting" value="-1" />
+        <!-- Evaluate assertions, requires running with "php -d zend.assertions=1 vendor/bin/phpunit" -->
+        <!-- <ini name="zend.assertions=1" value="1" /> -->
+        <ini name="assert.active" value="1" />
+        <ini name="assert.exception" value="1" />
+        <ini name="assert.bail" value="0" />
+    </php>
 </phpunit>
diff --git a/tests/IntegrationTest.php b/tests/IntegrationTest.php
index dfd15ce..7883740 100644
--- a/tests/IntegrationTest.php
+++ b/tests/IntegrationTest.php
@@ -151,6 +151,7 @@ public function testWaitingForRejectedConnectionShouldNotCreateAnyGarbageReferen
         $connector = new Connector(array('timeout' => false));
 
         gc_collect_cycles();
+        gc_collect_cycles(); // clear twice to avoid leftovers in PHP 7.4 with ext-xdebug and code coverage turned on
 
         $wait = true;
         $promise = $connector->connect('127.0.0.1:1')->then(