diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 97e71d7..3cbfe73 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -24,17 +24,22 @@ jobs:
           - 5.4
           - 5.3
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php }}
           coverage: xdebug
       - run: composer remove react/mysql --dev --no-interaction # do not install react/mysql example on legacy PHP
+      - name: Handle PHP 5.3 compatibility
         if: ${{ matrix.php == 5.3 }}
+        run: |
+          composer remove react/mysql react/promise-timer --dev --no-interaction
+          # Skip tests that require React\Promise\Timer
+          echo "PHPUNIT_ARGS=--exclude-group=internet" >> $GITHUB_ENV
       - run: composer install
-      - run: vendor/bin/phpunit --coverage-text
+      - run: vendor/bin/phpunit --coverage-text $PHPUNIT_ARGS
         if: ${{ matrix.php >= 7.3 }}
-      - run: vendor/bin/phpunit --coverage-text -c phpunit.xml.legacy
+      - run: vendor/bin/phpunit --coverage-text -c phpunit.xml.legacy $PHPUNIT_ARGS
         if: ${{ matrix.php < 7.3 }}
 
   PHPUnit-hhvm:
@@ -42,10 +47,13 @@ jobs:
     runs-on: ubuntu-18.04
     continue-on-error: true
     steps:
-      - uses: actions/checkout@v2
-      - uses: azjezz/setup-hhvm@v1
+      - uses: actions/checkout@v3
+      - run: cp "$(which composer)" composer.phar && ./composer.phar self-update --2.2 # downgrade Composer for HHVM
+      - name: Run HHVM Composer install
+        uses: docker://hhvm/hhvm:3.30-lts-latest
         with:
-          version: lts-3.30
-      - run: composer self-update --2.2 # downgrade Composer for HHVM
-      - run: hhvm $(which composer) install
-      - run: hhvm vendor/bin/phpunit
+          args: hhvm composer.phar remove react/mysql react/promise-timer --dev --no-interaction && hhvm composer.phar install
+      - name: Run HHVM PHPUnit
+        uses: docker://hhvm/hhvm:3.30-lts-latest
+        with:
+          args: hhvm vendor/bin/phpunit --exclude-group=internet
diff --git a/tests/FunctionalSshProcessConnectorTest.php b/tests/FunctionalSshProcessConnectorTest.php
index 1aaae23..e1a17c1 100644
--- a/tests/FunctionalSshProcessConnectorTest.php
+++ b/tests/FunctionalSshProcessConnectorTest.php
@@ -23,6 +23,17 @@ public function setUpConnector()
         $this->connector = new SshProcessConnector($url);
     }
 
+    /**
+     * @before
+     */
+    public function checkTimerSupport()
+    {
+        // Skip this test for PHP 5.3 where React\Promise\Timer isn't available
+        if (!class_exists('React\\Promise\\Timer')) {
+            $this->markTestSkipped('No Timer support available');
+        }
+    }
+
     public function testConnectInvalidProxyUriWillReturnRejectedPromise()
     {
         $this->connector = new SshProcessConnector(getenv('SSH_PROXY') . '.invalid');
diff --git a/tests/FunctionalSshSocksConnectorTest.php b/tests/FunctionalSshSocksConnectorTest.php
index 57ec2a1..86534cf 100644
--- a/tests/FunctionalSshSocksConnectorTest.php
+++ b/tests/FunctionalSshSocksConnectorTest.php
@@ -28,12 +28,28 @@ public function setUpConnector()
      */
     public function tearDownSSHClientProcess()
     {
+        // Skip timer-based teardown for PHP 5.3 where React\Promise\Timer is not available
+        if (!class_exists('React\\Promise\\Timer\\TimeoutException')) {
+            return;
+        }
+
         // run loop in order to shut down SSH client process again
         \React\Async\await(\React\Promise\Timer\sleep(0.001));
     }
 
+    // Helper method to check if Timer functions are available
+    private function hasTimerSupport()
+    {
+        return class_exists('React\\Promise\\Timer\\TimeoutException');
+    }
+
     public function testConnectInvalidProxyUriWillReturnRejectedPromise()
     {
+        if (!$this->hasTimerSupport()) {
+            $this->markTestSkipped('No Timer support available');
+            return;
+        }
+
         $this->connector = new SshSocksConnector(getenv('SSH_PROXY') . '.invalid');
 
         $promise = $this->connector->connect('example.com:80');
@@ -44,6 +60,11 @@ public function testConnectInvalidProxyUriWillReturnRejectedPromise()
 
     public function testConnectInvalidTargetWillReturnRejectedPromise()
     {
+        if (!$this->hasTimerSupport()) {
+            $this->markTestSkipped('No Timer support available');
+            return;
+        }
+
         $promise = $this->connector->connect('example.invalid:80');
 
         $this->setExpectedException('RuntimeException', 'Connection to tcp://example.invalid:80 failed because connection to proxy was lost');
@@ -52,6 +73,11 @@ public function testConnectInvalidTargetWillReturnRejectedPromise()
 
     public function testCancelConnectWillReturnRejectedPromise()
     {
+        if (!$this->hasTimerSupport()) {
+            $this->markTestSkipped('No Timer support available');
+            return;
+        }
+
         $promise = $this->connector->connect('example.com:80');
         $promise->cancel();
 
@@ -61,6 +87,11 @@ public function testCancelConnectWillReturnRejectedPromise()
 
     public function testConnectValidTargetWillReturnPromiseWhichResolvesToConnection()
     {
+        if (!$this->hasTimerSupport()) {
+            $this->markTestSkipped('No Timer support available');
+            return;
+        }
+
         $promise = $this->connector->connect('example.com:80');
 
         $connection = \React\Async\await(\React\Promise\Timer\timeout($promise, self::TIMEOUT));
@@ -73,6 +104,11 @@ public function testConnectValidTargetWillReturnPromiseWhichResolvesToConnection
 
     public function testConnectValidTargetWillReturnPromiseWhichResolvesToConnectionForCustomBindAddress()
     {
+        if (!$this->hasTimerSupport()) {
+            $this->markTestSkipped('No Timer support available');
+            return;
+        }
+
         $this->connector = new SshSocksConnector(getenv('SSH_PROXY') . '?bind=127.0.0.1:1081');
         $promise = $this->connector->connect('example.com:80');
 
@@ -86,6 +122,11 @@ public function testConnectValidTargetWillReturnPromiseWhichResolvesToConnection
 
     public function testConnectPendingWillNotInheritActiveFileDescriptors()
     {
+        if (!$this->hasTimerSupport()) {
+            $this->markTestSkipped('No Timer support available');
+            return;
+        }
+
         $server = stream_socket_server('tcp://127.0.0.1:0');
         $address = stream_socket_get_name($server, false);
 
diff --git a/tests/SshProcessConnectorTest.php b/tests/SshProcessConnectorTest.php
index d3a56d2..af0f83b 100644
--- a/tests/SshProcessConnectorTest.php
+++ b/tests/SshProcessConnectorTest.php
@@ -6,6 +6,26 @@
 
 class SshProcessConnectorTest extends TestCase
 {
+    /**
+     * @after
+     */
+    public function tearDownSSHClientProcess()
+    {
+        // Skip timer-based teardown for PHP 5.3 where React\Promise\Timer is not available
+        if (!class_exists('React\\Promise\\Timer\\TimeoutException')) {
+            return;
+        }
+
+        // run loop in order to shut down SSH client process again
+        \React\Async\await(\React\Promise\Timer\sleep(0.001));
+    }
+
+    // Helper method to check if Timer functions are available
+    private function hasTimerSupport()
+    {
+        return class_exists('React\\Promise\\Timer\\TimeoutException');
+    }
+
     public function testConstructWithoutLoopAssignsLoopAutomatically()
     {
         $connector = new SshProcessConnector('host');
@@ -104,6 +124,11 @@ public function testConstructorAcceptsHostWithLeadingDashWhenPrefixedWithUser()
 
     public function testConnectReturnsRejectedPromiseForInvalidUri()
     {
+        if (!$this->hasTimerSupport()) {
+            $this->markTestSkipped('No Timer support available');
+            return;
+        }
+
         $loop = $this->getMockBuilder('React\EventLoop\LoopInterface')->getMock();
         $connector = new SshProcessConnector('host', $loop);
 
@@ -113,6 +138,11 @@ public function testConnectReturnsRejectedPromiseForInvalidUri()
 
     public function testConnectReturnsRejectedPromiseForInvalidHost()
     {
+        if (!$this->hasTimerSupport()) {
+            $this->markTestSkipped('No Timer support available');
+            return;
+        }
+
         $loop = $this->getMockBuilder('React\EventLoop\LoopInterface')->getMock();
         $connector = new SshProcessConnector('host', $loop);