diff --git a/tests/test_adapters.py b/tests/test_adapters.py
index 97e28c797c..6c55d5a130 100644
--- a/tests/test_adapters.py
+++ b/tests/test_adapters.py
@@ -4,4 +4,5 @@
 def test_request_url_trims_leading_path_separators():
     """See also https://github.com/psf/requests/issues/6643."""
     a = requests.adapters.HTTPAdapter()
-    assert "/v:h" == a.request_url("http://127.0.0.1:10000//v:h", {})
+    p = requests.Request(method="GET", url="http://127.0.0.1:10000//v:h").prepare()
+    assert "/v:h" == a.request_url(p, {})