diff --git a/datasette/app.py b/datasette/app.py
index b89ab30c..6683d4dc 100644
--- a/datasette/app.py
+++ b/datasette/app.py
@@ -2462,7 +2462,7 @@ class Datasette:
     ):
         data = {"a": actor}
         if expire_after:
-            expires_at = int(time.time()) + (24 * 60 * 60)
+            expires_at = int(time.time()) + expire_after
             data["e"] = baseconv.base62.encode(expires_at)
         response.set_cookie("ds_actor", self.sign(data, "actor"))
 
diff --git a/tests/test_auth.py b/tests/test_auth.py
index e7a5402e..6024e3bb 100644
--- a/tests/test_auth.py
+++ b/tests/test_auth.py
@@ -524,3 +524,25 @@ async def test_root_without_root_enabled_no_special_permissions(ds_client):
         )
         is not True
     ), "Root without root_enabled should not automatically get set-column-type"
+
+
+@pytest.mark.parametrize("expire_after", (1, 300, 3600, 30 * 24 * 60 * 60))
+def test_set_actor_cookie_honours_expire_after(expire_after):
+    # GHSA-53fc-rhfg-h7qp issue 4: expire_after is documented as a number of
+    # seconds, but every value was being replaced with 24 hours.
+    from datasette.app import Datasette
+    from datasette.utils.asgi import Response
+
+    ds = Datasette(memory=True)
+    response = Response.text("")
+    before = int(time.time())
+    ds.set_actor_cookie(response, {"id": "test"}, expire_after=expire_after)
+    after = int(time.time())
+
+    (header,) = response._set_cookie_headers
+    assert header.startswith("ds_actor=")
+    value = header[len("ds_actor=") :].split(";", 1)[0]
+    data = ds.unsign(value, "actor")
+    assert data["a"] == {"id": "test"}
+    expires_at = baseconv.base62.decode(data["e"])
+    assert before + expire_after <= expires_at <= after + expire_after