diff --git a/requests_util/__init__.py b/requests_util/__init__.py
index 8dafd8d..ccefc71 100644
--- a/requests_util/__init__.py
+++ b/requests_util/__init__.py
@@ -79,8 +79,9 @@ def setup_limiter(
 
     Will always return the given session itself.
     """
-    if requests_ratelimiter:
+    if requests_ratelimiter and limiter_args:
         session.mount(url_prefix, requests_ratelimiter.LimiterAdapter(**limiter_args))
     if requests_cache and expire_after:
-        session.settings.urls_expire_after[url_prefix] = expire_after
+        if settings := getattr(session, 'settings', None):
+            settings.urls_expire_after[url_prefix] = expire_after
     return session