diff --git a/wp-admin/includes/post.php b/wp-admin/includes/post.php
index 48caefa4d9..ced29d4a72 100644
--- a/wp-admin/includes/post.php
+++ b/wp-admin/includes/post.php
@@ -2210,7 +2210,7 @@ function the_block_editor_meta_boxes() {
 	<?php the_block_editor_meta_box_post_form_hidden_fields( $post ); ?>
 	</form>
 	<?php foreach ( $locations as $location ) : ?>
-		<form class="metabox-location-<?php echo esc_attr( $location ); ?>">
+		<form class="metabox-location-<?php echo esc_attr( $location ); ?>" onsubmit="return false;">
 			<div id="poststuff" class="sidebar-open">
 				<div id="postbox-container-2" class="postbox-container">
 					<?php
diff --git a/wp-includes/version.php b/wp-includes/version.php
index ccd116e0d2..07041fc06d 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-alpha-44239';
+$wp_version = '5.1-alpha-44240';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.