diff --git a/tests/test_util.py b/tests/test_util.py
index dbc4050..0be2911 100644
--- a/tests/test_util.py
+++ b/tests/test_util.py
@@ -344,6 +344,15 @@ class TestGetLibUrl(TestCase):
 
     def test_buefy_css_custom(self):
 
+        # legacy prefix + deprecated setting name
+        self.config.setdefault(
+            "tailbone.liburl.buefy.css", "/lib/legacy-deprecated-buefy.css"
+        )
+        url = mod.get_liburl(self.request, "buefy_css", prefix="tailbone")
+        self.assertEqual(url, "/lib/legacy-deprecated-buefy.css")
+        url = mod.get_liburl(self.request, "buefy.css", prefix="tailbone")
+        self.assertEqual(url, "/lib/legacy-deprecated-buefy.css")
+
         # deprecated setting name
         self.config.setdefault("wuttaweb.liburl.buefy.css", "/lib/deprecated-buefy.css")
         url = mod.get_liburl(self.request, "buefy_css")