diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
index f4c4cc7879..3265691f7f 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
@@ -991,14 +991,16 @@ class WP_REST_Posts_Controller extends WP_REST_Controller {
 		}
 
 		// Parent.
-		if ( ! empty( $schema['properties']['parent'] ) && ! empty( $request['parent'] ) ) {
-			$parent = get_post( (int) $request['parent'] );
-
-			if ( empty( $parent ) ) {
-				return new WP_Error( 'rest_post_invalid_id', __( 'Invalid post parent ID.' ), array( 'status' => 400 ) );
+		if ( ! empty( $schema['properties']['parent'] ) && isset( $request['parent'] ) ) {
+			if ( 0 === (int) $request['parent'] ) {
+				$prepared_post->post_parent = 0;
+			} else {
+				$parent = get_post( (int) $request['parent'] );
+				if ( empty( $parent ) ) {
+					return new WP_Error( 'rest_post_invalid_id', __( 'Invalid post parent ID.' ), array( 'status' => 400 ) );
+				}
+				$prepared_post->post_parent = (int) $parent->ID;
 			}
-
-			$prepared_post->post_parent = (int) $parent->ID;
 		}
 
 		// Menu order.
diff --git a/tests/phpunit/tests/rest-api/rest-pages-controller.php b/tests/phpunit/tests/rest-api/rest-pages-controller.php
index a571803d12..b74d01c716 100644
--- a/tests/phpunit/tests/rest-api/rest-pages-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pages-controller.php
@@ -371,6 +371,41 @@ class WP_Test_REST_Pages_Controller extends WP_Test_REST_Post_Type_Controller_Te
 		$this->assertEquals( 0, $new_data['menu_order'] );
 	}
 
+	public function test_update_page_parent_non_zero() {
+		$page_id1 = $this->factory->post->create( array(
+			'post_type' => 'page',
+		) );
+		$page_id2 = $this->factory->post->create( array(
+			'post_type' => 'page',
+		) );
+		wp_set_current_user( self::$editor_id );
+		$request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/pages/%d', $page_id2 ) );
+		$request->set_body_params( array(
+			'parent' => $page_id1,
+		) );
+		$response = $this->server->dispatch( $request );
+		$new_data = $response->get_data();
+		$this->assertEquals( $page_id1, $new_data['parent'] );
+	}
+
+	public function test_update_page_parent_zero() {
+		$page_id1 = $this->factory->post->create( array(
+			'post_type' => 'page',
+		) );
+		$page_id2 = $this->factory->post->create( array(
+			'post_type'    => 'page',
+			'post_parent'  => $page_id1,
+		) );
+		wp_set_current_user( self::$editor_id );
+		$request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/pages/%d', $page_id2 ) );
+		$request->set_body_params( array(
+			'parent' => 0,
+		) );
+		$response = $this->server->dispatch( $request );
+		$new_data = $response->get_data();
+		$this->assertEquals( 0, $new_data['parent'] );
+	}
+
 	public function test_get_page_with_password() {
 		$page_id = $this->factory->post->create( array(
 			'post_type'     => 'page',