diff --git a/source/c04/p01_manually_consuming_iterator.rst b/source/c04/p01_manually_consuming_iterator.rst
index 35e1904..190b5e5 100644
--- a/source/c04/p01_manually_consuming_iterator.rst
+++ b/source/c04/p01_manually_consuming_iterator.rst
@@ -32,7 +32,7 @@
 
     with open('/etc/passwd') as f:
         while True:
-            line = next(f)
+            line = next(f, None)
             if line is None:
                 break
             print(line, end='')