diff --git a/book/book.tex b/book/book.tex
index 10b67ce7..519b19c2 100644
--- a/book/book.tex
+++ b/book/book.tex
@@ -7263,7 +7263,7 @@ \section{Implementation of Schelling's model}
 \end{code}
 
 Then I use \py{correlate2d} to count, for each location,
-the number of neighboring cells that are red, blue, and non-empty.
+the number of neighboring cells that are red, blue, and empty.
 We saw \py{correlate2d} in Section~\ref{implife}.
 
 \index{SciPy}