diff --git a/qutebrowser/browser/adblock.py b/qutebrowser/browser/adblock.py
index e265b74f0..54c8ce28f 100644
--- a/qutebrowser/browser/adblock.py
+++ b/qutebrowser/browser/adblock.py
@@ -66,7 +66,7 @@ def is_whitelisted_host(url):
     """Check if the given url is on the adblock whitelist.
 
     Args:
-        url: The url to check.
+        url: The url to check as a string.
     """
     for pattern in config.val.content.host_blocking.whitelist:
         if urlmatch.URLPattern(pattern).matches(url):