diff --git a/tests/bulk/bulkwrite-delete-001.phpt b/tests/bulk/bulkwrite-delete-001.phpt
index b0bae3521..d8a999b84 100644
--- a/tests/bulk/bulkwrite-delete-001.phpt
+++ b/tests/bulk/bulkwrite-delete-001.phpt
@@ -13,7 +13,7 @@ class MyClass implements MongoDB\BSON\Persistable
     private $id;
     private $child;
 
-    public function __construct($id, MyClass $child = null)
+    public function __construct($id, ?MyClass $child = null)
     {
         $this->id = $id;
         $this->child = $child;
diff --git a/tests/bulk/bulkwrite-insert-001.phpt b/tests/bulk/bulkwrite-insert-001.phpt
index 4160a95f8..b2e57b11b 100644
--- a/tests/bulk/bulkwrite-insert-001.phpt
+++ b/tests/bulk/bulkwrite-insert-001.phpt
@@ -13,7 +13,7 @@ class MyClass implements MongoDB\BSON\Persistable
     private $id;
     private $child;
 
-    public function __construct($id, MyClass $child = null)
+    public function __construct($id, ?MyClass $child = null)
     {
         $this->id = $id;
         $this->child = $child;
diff --git a/tests/bulk/bulkwrite-update-001.phpt b/tests/bulk/bulkwrite-update-001.phpt
index a02a78a90..e6e530984 100644
--- a/tests/bulk/bulkwrite-update-001.phpt
+++ b/tests/bulk/bulkwrite-update-001.phpt
@@ -13,7 +13,7 @@ class MyClass implements MongoDB\BSON\Persistable
     private $id;
     private $child;
 
-    public function __construct($id, MyClass $child = null)
+    public function __construct($id, ?MyClass $child = null)
     {
         $this->id = $id;
         $this->child = $child;
diff --git a/tests/command/command-ctor-001.phpt b/tests/command/command-ctor-001.phpt
index 024b34d96..7716abb52 100644
--- a/tests/command/command-ctor-001.phpt
+++ b/tests/command/command-ctor-001.phpt
@@ -13,7 +13,7 @@ class MyClass implements MongoDB\BSON\Persistable
     private $id;
     private $child;
 
-    public function __construct($id, MyClass $child = null)
+    public function __construct($id, ?MyClass $child = null)
     {
         $this->id = $id;
         $this->child = $child;
diff --git a/tests/query/query-ctor-001.phpt b/tests/query/query-ctor-001.phpt
index 98861f87c..b2f88a1d4 100644
--- a/tests/query/query-ctor-001.phpt
+++ b/tests/query/query-ctor-001.phpt
@@ -13,7 +13,7 @@ class MyClass implements MongoDB\BSON\Persistable
     private $id;
     private $child;
 
-    public function __construct($id, MyClass $child = null)
+    public function __construct($id, ?MyClass $child = null)
     {
         $this->id = $id;
         $this->child = $child;
diff --git a/tests/utils/tools.php b/tests/utils/tools.php
index e308e3e5c..07142cc32 100644
--- a/tests/utils/tools.php
+++ b/tests/utils/tools.php
@@ -92,7 +92,7 @@ function get_module_info($row)
     return $matches[1];
 }
 
-function create_test_manager(string $uri = null, array $options = [], array $driverOptions = [])
+function create_test_manager(?string $uri = null, array $options = [], array $driverOptions = [])
 {
     if (getenv('API_VERSION') && ! isset($driverOptions['serverApi'])) {
         $driverOptions['serverApi'] = new ServerApi(getenv('API_VERSION'));
@@ -628,7 +628,7 @@ function severityToString(int $severity): string {
  * from a particular function. Returns the message from the raised error or
  * exception, or an empty string if neither was thrown.
  */
-function raises(callable $callable, int $expectedSeverity, string $expectedFromFunction = null): string
+function raises(callable $callable, int $expectedSeverity, ?string $expectedFromFunction = null): string
 {
     set_error_handler(function(int $severity, string $message, string $file, int $line) {
         throw new ErrorException($message, 0, $severity, $file, $line);
@@ -672,7 +672,7 @@ function raises(callable $callable, int $expectedSeverity, string $expectedFromF
  * the exception to be thrown from a particular function. Returns the message
  * from the thrown exception, or an empty string if one was not thrown.
  */
-function throws(callable $callable, string $expectedException, string $expectedFromFunction = null): string
+function throws(callable $callable, string $expectedException, ?string $expectedFromFunction = null): string
 {
     try {
         call_user_func($callable);
@@ -730,7 +730,7 @@ function printWriteResult(WriteResult $result, $details = true)
     }
 }
 
-function printWriteConcernError(WriteConcernError $error = null, $details)
+function printWriteConcernError(?WriteConcernError $error = null, $details = null)
 {
     if ($error) {
         /* This stuff is generated by the server, no need for us to test it */