diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 81d668d..cf8a654 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -15,7 +15,9 @@ jobs:
   build:
     strategy:
       matrix:
-        php: ['8.0', '8.3']
+        php:
+          - '8.4'
+          - '8.0'
       fail-fast: false
     name: Tests / PHP ${{ matrix.php }}
     runs-on: ubuntu-latest
diff --git a/src/MetaQuery/Query.php b/src/MetaQuery/Query.php
index 039ffdb..583989b 100644
--- a/src/MetaQuery/Query.php
+++ b/src/MetaQuery/Query.php
@@ -44,7 +44,7 @@ final public static function fromArray( array $clauses ) : self {
 		return $class;
 	}
 
-	final public function addClause( Clause $clause, string $key = null ) : void {
+	final public function addClause( Clause $clause, ?string $key = null ) : void {
 		if ( null !== $key ) {
 			$this->clauses[ $key ] = $clause;
 		} else {
diff --git a/tests/WP_Block_Type.php b/tests/WP_Block_Type.php
index 3fe4567..68ce446 100644
--- a/tests/WP_Block_Type.php
+++ b/tests/WP_Block_Type.php
@@ -40,7 +40,7 @@
 		'align' => 'left',
 	],
 ];
-$args->render_callback = function( array $atts, string $content, WP_Block $block = null ) {
+$args->render_callback = function( array $atts, string $content, ?WP_Block $block = null ) {
 	return $content;
 };
 $args->attributes = [