diff --git a/src/wp-admin/edit-form-blocks.php b/src/wp-admin/edit-form-blocks.php
index 3a399c2fcdfd0..fa4b8a9dd17e6 100644
--- a/src/wp-admin/edit-form-blocks.php
+++ b/src/wp-admin/edit-form-blocks.php
@@ -119,7 +119,7 @@ function( $classes ) {
  * besides the default value.
  */
 $available_templates = wp_get_theme()->get_page_templates( get_post( $post->ID ) );
-$available_templates = ! empty( $available_templates ) ? array_merge(
+$available_templates = ! empty( $available_templates ) ? array_replace(
 	array(
 		/** This filter is documented in wp-admin/includes/meta-boxes.php */
 		'' => apply_filters( 'default_page_template_title', __( 'Default template' ), 'rest-api' ),