diff --git a/src/wp-includes/class-wp-editor.php b/src/wp-includes/class-wp-editor.php
index 916be4d9d4..1d2c75c113 100644
--- a/src/wp-includes/class-wp-editor.php
+++ b/src/wp-includes/class-wp-editor.php
@@ -681,8 +681,10 @@ final class _WP_Editors {
 						$body_class .= ' post-format-standard';
 				}
 
-				if ( $page_template = get_page_template_slug( $post ) ) {
-					$page_template = str_replace( '.', '-', basename( $page_template, '.php' ) );
+				$page_template = get_page_template_slug( $post );
+
+				if ( $page_template !== false ) {
+					$page_template = empty( $page_template ) ? 'default' : str_replace( '.', '-', basename( $page_template, '.php' ) );
 					$body_class .= ' page-template-' . sanitize_html_class( $page_template );
 				}
 			}