diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
index f4c4cc7879..3265691f7f 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
+++ b/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/wp-includes/version.php b/wp-includes/version.php
index 18d4737f3d..d192da5b12 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-beta4-39288';
+$wp_version = '4.7-beta4-39289';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.