Fixed small typo Pointed out by Michael Hudson.
diff --git a/Doc/ext/newtypes.tex b/Doc/ext/newtypes.tex
index cfc76b8..6b8a25d 100644
--- a/Doc/ext/newtypes.tex
+++ b/Doc/ext/newtypes.tex
@@ -255,7 +255,7 @@
 That wasn't so hard, was it?
 
 Of course, the current Noddy type is pretty uninteresting. It has no
-data and doesn't do anything. It can't even be subclasses.
+data and doesn't do anything. It can't even be subclassed.
 
 \subsection{Adding data and methods to the Basic example}