diff --git a/tests/test_app.py b/tests/test_app.py
index d13f5e9..e607685 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -296,3 +296,21 @@ def test_sitemap_and_open_graph(client, cfg):
     assert sm.status_code == 200
     assert "<loc>https://blog.example.no/</loc>" in sm.text
     assert "<loc>https://blog.example.no/og-test/</loc>" in sm.text
+
+
+def test_base_path_derived_from_site_url(tmp_path):
+    cfg = load_config(
+        {"SOAPBOX_DATA_DIR": str(tmp_path / "a"), "SOAPBOX_SITE_URL": "https://x.no/blog/"}
+    )
+    assert cfg.base_path == "/blog" and cfg.site_url == "https://x.no/blog"
+    cfg = load_config({"SOAPBOX_DATA_DIR": str(tmp_path / "b"), "SOAPBOX_SITE_URL": "https://x.no"})
+    assert cfg.base_path == ""
+    # eksplisitt tom verdi overstyrer (proxy stripper prefikset)
+    cfg = load_config(
+        {
+            "SOAPBOX_DATA_DIR": str(tmp_path / "c"),
+            "SOAPBOX_SITE_URL": "https://x.no/blog",
+            "SOAPBOX_BASE_PATH": "",
+        }
+    )
+    assert cfg.base_path == ""