diff --git a/src/Redmine/Serializer/XmlSerializer.php b/src/Redmine/Serializer/XmlSerializer.php
index f0b10050..5d686136 100644
--- a/src/Redmine/Serializer/XmlSerializer.php
+++ b/src/Redmine/Serializer/XmlSerializer.php
@@ -144,9 +144,9 @@ private function denormalize(array $normalized): void
     }
 
     /**
-     * @param array<mixed> $params
+     * @param string|array<mixed> $params
      */
-    private function createXmlElement(string $rootElementName, array $params): SimpleXMLElement
+    private function createXmlElement(string $rootElementName, $params): SimpleXMLElement
     {
         $value = '';
         if (! is_array($params)) {
diff --git a/tests/Integration/Psr18ClientRequestGenerationTest.php b/tests/Integration/Psr18ClientRequestGenerationTest.php
index c98edbe6..1d98fe5a 100644
--- a/tests/Integration/Psr18ClientRequestGenerationTest.php
+++ b/tests/Integration/Psr18ClientRequestGenerationTest.php
@@ -69,7 +69,7 @@ public function testPsr18ClientCreatesCorrectRequests(
             return new Request($method, $uri);
         });
 
-        $streamFactory = new class () implements StreamFactoryInterface {
+        $streamFactory = new class implements StreamFactoryInterface {
             public function createStream(string $content = ''): StreamInterface
             {
                 return Utils::streamFor($content);
diff --git a/tests/Unit/Client/NativeCurlClientTest.php b/tests/Unit/Client/NativeCurlClientTest.php
index 0cfd6c8b..1f4c234d 100644
--- a/tests/Unit/Client/NativeCurlClientTest.php
+++ b/tests/Unit/Client/NativeCurlClientTest.php
@@ -767,7 +767,7 @@ public function testGetApiShouldThrowException(): void
         );
 
         $this->expectException(InvalidArgumentException::class);
-        $this->expectExceptionMessage('`do_not_exist` is not a valid api. Possible apis are `attachment`, `group`, `custom_fields`, `issue`, `issue_category`, `issue_priority`, `issue_relation`, `issue_status`, `membership`, `news`, `project`, `query`, `role`, `time_entry`, `time_entry_activity`, `tracker`, `user`, `version`, `wiki`, `search`');
+        $this->expectExceptionMessage('`do_not_exist` is not a valid api. Possible apis are `attachment`, `group`, `custom_fields`, `issue`, `issue_category`, `issue_priority`, `issue_relation`, `issue_status`, `membership`, `news`, `project`, `query`, `role`, `search`, `time_entry`, `time_entry_activity`, `tracker`, `user`, `version`, `wiki`');
 
         $client->getApi('do_not_exist');
     }
diff --git a/tests/Unit/Client/Psr18ClientTest.php b/tests/Unit/Client/Psr18ClientTest.php
index fd1f260c..3f5b6592 100644
--- a/tests/Unit/Client/Psr18ClientTest.php
+++ b/tests/Unit/Client/Psr18ClientTest.php
@@ -303,7 +303,7 @@ public function testGetApiShouldThrowException(): void
         );
 
         $this->expectException(InvalidArgumentException::class);
-        $this->expectExceptionMessage('`do_not_exist` is not a valid api. Possible apis are `attachment`, `group`, `custom_fields`, `issue`, `issue_category`, `issue_priority`, `issue_relation`, `issue_status`, `membership`, `news`, `project`, `query`, `role`, `time_entry`, `time_entry_activity`, `tracker`, `user`, `version`, `wiki`, `search`');
+        $this->expectExceptionMessage('`do_not_exist` is not a valid api. Possible apis are `attachment`, `group`, `custom_fields`, `issue`, `issue_category`, `issue_priority`, `issue_relation`, `issue_status`, `membership`, `news`, `project`, `query`, `role`, `search`, `time_entry`, `time_entry_activity`, `tracker`, `user`, `version`, `wiki`');
 
         $client->getApi('do_not_exist');
     }
diff --git a/tests/Unit/Serializer/JsonSerializerTest.php b/tests/Unit/Serializer/JsonSerializerTest.php
index 58c2ae65..81f7df7c 100644
--- a/tests/Unit/Serializer/JsonSerializerTest.php
+++ b/tests/Unit/Serializer/JsonSerializerTest.php
@@ -63,7 +63,7 @@ public static function getEncodedToNormalizedData(): array
      * @dataProvider getEncodedToNormalizedData
      */
     #[DataProvider('getEncodedToNormalizedData')]
-    public function testCreateFromStringDecodesToExpectedNormalizedData(string $data, string $expected): void
+    public function testCreateFromStringDecodesToExpectedNormalizedData(string $data, $expected): void
     {
         $serializer = JsonSerializer::createFromString($data);
 
@@ -184,7 +184,7 @@ public static function getNormalizedToEncodedData(): array
      * @dataProvider getNormalizedToEncodedData
      */
     #[DataProvider('getNormalizedToEncodedData')]
-    public function testCreateFromArrayEncodesToExpectedString(array $data, string $expected): void
+    public function testCreateFromArrayEncodesToExpectedString(array $data, $expected): void
     {
         $serializer = JsonSerializer::createFromArray($data);