diff --git a/wp-admin/includes/post.php b/wp-admin/includes/post.php
index 7a1e2a81b4..0e19876e51 100644
--- a/wp-admin/includes/post.php
+++ b/wp-admin/includes/post.php
@@ -610,9 +610,11 @@ function bulk_edit_posts( $post_data = null ) {
 
 		if ( isset( $shared_post_data['post_format'] ) ) {
 			set_post_format( $post_ID, $shared_post_data['post_format'] );
-			unset( $post_data['tax_input']['post_format'] );
 		}
 
+		// Prevent wp_insert_post() from overwriting post format with the old data.
+		unset( $post_data['tax_input']['post_format'] );
+
 		$updated[] = wp_update_post( $post_data );
 
 		if ( isset( $post_data['sticky'] ) && current_user_can( $ptype->cap->edit_others_posts ) ) {
diff --git a/wp-includes/version.php b/wp-includes/version.php
index ae3adbeb18..625bb0c6f3 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-beta1-44669';
+$wp_version = '5.1-beta1-44670';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.