diff --git a/wp-db-backup.php b/wp-db-backup.php
index eb23d0b..e5e3576 100755
--- a/wp-db-backup.php
+++ b/wp-db-backup.php
@@ -109,7 +109,10 @@ function __construct() {
 			}
 		}
 
-		$requested_temp_dir = sanitize_text_field($_GET['wp_db_temp_dir']);
+		$requested_temp_dir = '';
+		if (array_key_exists('wp_db_temp_dir', $_GET)) {
+			$requested_temp_dir = sanitize_text_field($_GET['wp_db_temp_dir']);
+		}
 		$this->backup_dir = trailingslashit(apply_filters('wp_db_b_backup_dir', (isset($requested_temp_dir) && is_writable($requested_temp_dir)) ? $requested_temp_dir : get_temp_dir()));
 		$this->basename = 'wp-db-backup';