diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index 0273eea26b8..afadd9b35a3 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -698,6 +698,7 @@ in the `project-current' call, the timeout is determined by
            vc-handled-backends))
          project)
     (while (and
+            root
             (eq backend 'Git)
             (project--vc-merge-submodules-p root)
             (project--submodule-p root))