diff --git a/book_format.py b/book_format.py
index 100dd51..55fdd7d 100644
--- a/book_format.py
+++ b/book_format.py
@@ -12,7 +12,7 @@ sys.path.insert(0,'./code') # allow us to import book_format
 
 def test_filterpy_version():
     import filterpy
-    min_version = [0,0,21]
+    min_version = [0,0,22]
     v = filterpy.__version__
     tokens = v.split('.')
     for i,v in enumerate(tokens):