diff --git a/linkcheck/UrlData.py b/linkcheck/UrlData.py
index 36bbc063..730239d2 100644
--- a/linkcheck/UrlData.py
+++ b/linkcheck/UrlData.py
@@ -383,7 +383,7 @@ class UrlData:
         if sizebytes >= self.config["warnsizebytes"]:
             self.setWarning(linkcheck._("Content size %s is larger than %s")%\
                          (StringUtil.strsize(sizebytes),
-                          StringUtil.strsize(self.config["warnsizebytes"]))
+                          StringUtil.strsize(self.config["warnsizebytes"])))
 
 
     def parseUrl (self):