diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index 6c50135358..5eee20e408 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -863,8 +863,12 @@ project-find-file
 for VCS directories listed in `vc-directory-exclusion-list'."
   (interactive "P")
   (let* ((pr (project-current t))
-         (dirs (list (project-root pr))))
-    (project-find-file-in (thing-at-point 'filename) dirs pr include-all)))
+         (root (project-root pr))
+         (dirs (list root)))
+    (project-find-file-in
+     (or (thing-at-point 'filename)
+         (and buffer-file-name (file-relative-name buffer-file-name root)))
+     dirs pr include-all)))
 
 ;;;###autoload
 (defun project-or-external-find-file (&optional include-all)