diff --git a/Lib/calendar.py b/Lib/calendar.py
index 723bb3c..db7b2b6 100644
--- a/Lib/calendar.py
+++ b/Lib/calendar.py
@@ -256,7 +256,7 @@
     similar to the UNIX program cal.
     """
 
-    def prweek(theweek, width):
+    def prweek(self, theweek, width):
         """
         Print a single week (no newline).
         """