diff --git a/wp-includes/class-wp-editor.php b/wp-includes/class-wp-editor.php
index 916be4d9d4..1d2c75c113 100644
--- a/wp-includes/class-wp-editor.php
+++ b/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 );
 				}
 			}
diff --git a/wp-includes/version.php b/wp-includes/version.php
index f5428b5683..8de301bb23 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.8-alpha-39677';
+$wp_version = '4.8-alpha-39678';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.