diff --git a/src/wp-includes/class-wp-xmlrpc-server.php b/src/wp-includes/class-wp-xmlrpc-server.php
index 513bd1cdbf..10fe6605cc 100644
--- a/src/wp-includes/class-wp-xmlrpc-server.php
+++ b/src/wp-includes/class-wp-xmlrpc-server.php
@@ -1412,19 +1412,19 @@ class wp_xmlrpc_server extends IXR_Server {
 		$defaults = array(
 			'post_status'    => 'draft',
 			'post_type'      => 'post',
-			'post_author'    => null,
-			'post_password'  => null,
-			'post_excerpt'   => null,
-			'post_content'   => null,
-			'post_title'     => null,
-			'post_date'      => null,
-			'post_date_gmt'  => null,
+			'post_author'    => 0,
+			'post_password'  => '',
+			'post_excerpt'   => '',
+			'post_content'   => '',
+			'post_title'     => '',
+			'post_date'      => '',
+			'post_date_gmt'  => '',
 			'post_format'    => null,
 			'post_name'      => null,
 			'post_thumbnail' => null,
-			'post_parent'    => null,
-			'ping_status'    => null,
-			'comment_status' => null,
+			'post_parent'    => 0,
+			'ping_status'    => '',
+			'comment_status' => '',
 			'custom_fields'  => null,
 			'terms_names'    => null,
 			'terms'          => null,
@@ -1499,11 +1499,11 @@ class wp_xmlrpc_server extends IXR_Server {
 			$post_data['post_author'] = $user->ID;
 		}
 
-		if ( isset( $post_data['comment_status'] ) && 'open' !== $post_data['comment_status'] && 'closed' !== $post_data['comment_status'] ) {
+		if ( 'open' !== $post_data['comment_status'] && 'closed' !== $post_data['comment_status'] ) {
 			unset( $post_data['comment_status'] );
 		}
 
-		if ( isset( $post_data['ping_status'] ) && 'open' !== $post_data['ping_status'] && 'closed' !== $post_data['ping_status'] ) {
+		if ( 'open' !== $post_data['ping_status'] && 'closed' !== $post_data['ping_status'] ) {
 			unset( $post_data['ping_status'] );
 		}
 
@@ -1681,6 +1681,14 @@ class wp_xmlrpc_server extends IXR_Server {
 		 */
 		$post_data = apply_filters( 'xmlrpc_wp_insert_post_data', $post_data, $content_struct );
 
+		// Remove all null values to allow for using the insert/update post default values for those keys instead.
+		$post_data = array_filter(
+			$post_data,
+			static function ( $value ) {
+				return null !== $value;
+			}
+		);
+
 		$post_ID = $update ? wp_update_post( $post_data, true ) : wp_insert_post( $post_data, true );
 		if ( is_wp_error( $post_ID ) ) {
 			return new IXR_Error( 500, $post_ID->get_error_message() );
diff --git a/tests/phpunit/tests/date/xmlrpc.php b/tests/phpunit/tests/date/xmlrpc.php
index 3258909cfb..63daeb41da 100644
--- a/tests/phpunit/tests/date/xmlrpc.php
+++ b/tests/phpunit/tests/date/xmlrpc.php
@@ -24,16 +24,6 @@ class Tests_Date_XMLRPC extends WP_XMLRPC_UnitTestCase {
 	 * @covers wp_xmlrpc_server::mw_newPost
 	 */
 	public function test_date_new_post() {
-		if ( PHP_VERSION_ID >= 80100 ) {
-			/*
-			 * For the time being, ignoring PHP 8.1 "null to non-nullable" deprecations coming in
-			 * via hooked in filter functions until a more structural solution to the
-			 * "missing input validation" conundrum has been architected and implemented.
-			 */
-			$this->expectDeprecation();
-			$this->expectDeprecationMessageMatches( '`Passing null to parameter \#[0-9]+ \(\$[^\)]+\) of type [^ ]+ is deprecated`' );
-		}
-
 		$timezone = 'Europe/Helsinki';
 		update_option( 'timezone_string', $timezone );