diff --git a/src/Job/Message.php b/src/Job/Message.php
index 66c731e..02552c6 100644
--- a/src/Job/Message.php
+++ b/src/Job/Message.php
@@ -96,7 +96,7 @@ public function getParsedBody(): array
      *
      * @return \Closure
      */
-    public function getCallable()
+    public function getCallable(): Closure
     {
         if ($this->callable) {
             return $this->callable;
@@ -140,7 +140,7 @@ public function getTarget(): array
      * @param mixed $default Default value.
      * @return mixed
      */
-    public function getArgument($key = null, $default = null)
+    public function getArgument(mixed $key = null, mixed $default = null)
     {
         if (array_key_exists('data', $this->parsedBody)) {
             $data = $this->parsedBody['data'];
@@ -175,7 +175,7 @@ public function getMaxAttempts(): ?int
      * @return string
      * @psalm-suppress InvalidToString
      */
-    public function __toString()
+    public function __toString(): string
     {
         return (string)json_encode($this);
     }
@@ -184,7 +184,7 @@ public function __toString()
      * @return array
      */
     #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    public function jsonSerialize(): array
     {
         return $this->parsedBody;
     }
diff --git a/tests/TestCase/Job/MessageTest.php b/tests/TestCase/Job/MessageTest.php
index e828814..47e56c3 100644
--- a/tests/TestCase/Job/MessageTest.php
+++ b/tests/TestCase/Job/MessageTest.php
@@ -31,7 +31,7 @@ class MessageTest extends TestCase
      *
      * @return void
      */
-    public function testConstructorAndGetters()
+    public function testConstructorAndGetters(): void
     {
         $callable = ['TestApp\WelcomeMailer', 'welcome'];
         $time = 'sample data ' . time();
@@ -69,7 +69,7 @@ public function testConstructorAndGetters()
      *
      * @return void
      */
-    public function testLegacyArguments()
+    public function testLegacyArguments(): void
     {
         $callable = ['TestApp\WelcomeMailer', 'welcome'];
         $args = [
@@ -98,7 +98,7 @@ public function testLegacyArguments()
      *
      * @return void
      */
-    public function testGetCallableInvalidClass()
+    public function testGetCallableInvalidClass(): void
     {
         $parsedBody = [
             'class' => ['Trash', 'trash'],
@@ -120,7 +120,7 @@ public function testGetCallableInvalidClass()
      *
      * @return void
      */
-    public function testGetCallableInvalidType()
+    public function testGetCallableInvalidType(): void
     {
         $parsedBody = [
             'class' => ['TestApp\WelcomeMailer', 'trash', 'oops'],