diff --git a/test/lisp/tab-bar-tests.el b/test/lisp/tab-bar-tests.el
index e0de25bdc39..18ca9fee8a4 100644
--- a/test/lisp/tab-bar-tests.el
+++ b/test/lisp/tab-bar-tests.el
@@ -52,6 +52,7 @@
   (tab-bar-tabs-set nil))
 
 (ert-deftest tab-bar-tests-quit-restore-window ()
+  :tags '(:unstable)                    ; Can hang.
   (skip-when (pcase system-type
                ;; Skip test on MS-Windows in batch mode, since terminal
                ;; frames cannot be created in that case.